I personally have no problem really with systems where your weapons and equipment degrade and eventually break compleatly... but I don't expect it to be in every game. In some games it just does not make sence to have things like durability, where as in others it does.
For me, Cyberpunk is one such game where it could make sence. Exactly to what degree of a durability system they should use for it... that I don't really know... but I have a system in mind that could work.
Rather than have the weapons compleatly break, so that you can not use them anymore untill they are repaired, why not use a system where when the weapon starts getting into bad shape (and/or get's realy dirty) it starts to malfunction at times... malfunctions which you have to fix befor you can fire again (either by using the reload key or maybe a seperate key for racking the gun, etc)... and eventually it even becomes less reliable in accuracy due to it becoming missaligned. That way you will never reach a point where you can not continue the fight because your weapon broke or something, yes your weapon starts to become a bit more unreliabe, but you can still continue to fight with it.
It could also introduce some pretty interesting scenarios if you had to keep fighting so long (or you have to start using the opponents weapons, because you did not bring enough ammunition or something yourself, and their weapons might not be in as good of a shape as one would like), so that your weapons starts to act up on you. Like that crucial moment where you maybe have finally found your target, and you find a good sniping possition or something... but due to that the gun is in bad shape your aimed headshot randomly missed it's target, which of course compleatly alerts them to your prescence, where they then maybe tries to flee, or maybe calls in backup to fight back. Or how about rounding a corner only to find your self infront of an enemy, you aim your weapon to fire, and as you pull the trigger it clicks on you (or what ever other sound a malfunction might make), followed by a scramble from you to either get into cover again to fix the problem, or fix the problem right there and hoping the opponent does not react in time.
I see 4 "stages" of a state that your weapon can be in (this is mostly for guns... but if you change the wording etc I guess it could fit for anything):
1: Perfect condition. The weapon works as it should. How long it does, I don't know... maybe it lasts an entire standard mission length, or maybe 2-3+ of them.
2: Dirty. The gun starts to missfire evey now and then, where you have to fix it befor being able to fire again. Maybe a 1-5% chans for each bullet fired.
3: Worn (+ really Dirty). The missfire rate is increased, to such a level where it becomes a real problem. ~5-20'ish % chance per bullet shot maybe.
4: Misaligned (+ Really Worn, + Extremelly Dirty). The guns accuracy goes down, where at times the shot will randomly deviate X% from where you aimed it, which can potentualy lead to that you miss (and potentually hit something/someone your not supposed to due to it... suddenly taking that shot to save a hostage who is being held at gunpoint becomes a problem). The gun now also has a serious problem of missfiring, maybe somewhere around the 10-35'ish % per bullet fired.
As for repairing/cleaning/realigning a weapon again to be in top condition, that I don't think you should be able to do "in the field"... because such a thing tends to take a fairly large amount of time to do, especialy if you need to start to realigning your gun back to being as accurate as it can be. You need to be at home, or at a weaponshop to do that I feel. And when you do it, it advances the ingame time forward with X amount depending on what level of fix you needed to do. If you clean a weapon which is still in Stage 1, it takes maybe 30 minuts. Cleaning a weapon in Stage 2, also takes 30 minuts. Fixing and cleaning a weapon in Stage 3 takes ~ an hour. A weapon in Stage 4 needs to be realigned (+cleaned and fixing worn things on top of that), and depending on how bad it has goten it will take maybe 2-3 hours to fix.
In my mind what you can and can not do at home will highly depend on if you have the right equipment or not. Stage 1 and 2 can always be fixed at home, but if you lack the normally required equipment it doubles the time it takes. Stage 3 can be done at home if you have the required equipment, if you do not then you have to do it at a weaponstore. Stage 4 can only be fixed at a weaponstore.
Lacking/having the right abilities (Repair and/or Gunsmithing etc) could potentually also effect the times it takes to do these things, and some Stages might be locked out for your character to do them selves if they do not have the skills. For example, if you lack any ability that deals with these things, then the only thing your character can do them selves is cleaning the weapons as Stage 1 and 2, but the time it takes is doubled (which means if you lack the skills needed, and lack the right equipment, then cleaning a weapon at stage 1 and 2 would take 2 hours). If you lack the skill "Repair" (and/or other relevant skill), then you can not perform the repairs needed for a weapon at Stage 3, you will have to go to a shop and pay X amount of money for it. As for Stage 4, no matter if you have the skills or not you still need to go to a weaponstore to do it... but if you do have the skill/skills you can choice to try and fix it your self (at a reduced cost of course since your renting the use of their facilities and tools).
Letting a store fix these things for you will always be a 100% successrate, which means it will always take the minimum amount of time needed for each Stage, but will cost you a lot more money to do compared to if you bought the required equipment and did the fixes yourself. Doing the things yourself will be cheaper compared to if you let the store do it, but can result in a "failure" when the dice is rolled for the relevant skill, but the only real outcome of that is that it takes you longer to fix the problem.
This could potentualy be an important thing as well.. the time it takes to fix things, and the chance that it might take longer if you fail... and that a store will always take the minimum amount of time but will cost you more. Because you are maybe pressed for time for a mission, so maybe it might be better to take the 100% chance of it taking the minimum mount of time by paying a lot more money to have the weaponstore do it... because if you did it your self there might always be at the very least a 5% chance or so that you would fail (I always prefer it if rpg games leaves atleast 5% chance to fail on things, no matter how good your character is at it), resulting in it taking longer to fix, which could potentualy result in a failed mission because you got there to late.
Granted... I think some might find this, weapon becoming inaccurate and starting to missfire on you due to weapon being in a bad shape, and all my suggested repair rules and what not... to be a lot more annoying then for example you being compleatly unable to use a weapon because you went down to 0 in durability on it, and needing to repair it befor use again. But I think that is the point really... or atleast part of it. That it should be annoying when your weapon starts to act up on you, so that you try and always keep your weapons in as good of a condition as you can at all times... but that at times you might not have had chance to fix it properly, so you have to deal with your situation at hand.
I think the upside to my suggestion, that weapons don't really break so that you can no longer use them, where you just have to deal with a missbehaving weapon untill your in a possition to get it fixed... is that you can keep going as long as you have the ammunition for it. Or find a temporary/permanent replacement or something (even if the replacemebt is not as good) because you just cant be without a main weapon or something in your current situation.