Actual Satchel Charges that you can place and find or buy from vendors. You can now set up a killzone or place an ambush and detonate the explosion to wipe out tons of enemies at once. Also a Sticky and Proximity setting for explosives.
I'm not exactly sure what you're referring to with the satchel. To me it sounds like you want to restrict the amount of grenades etc your can carry from the start and 'unlock' added space by upgrading the satchel?
To be honest, I would not mind this, running around with 300+ grenades that I rarely use feels a bit weird.
As far as your second notion.
grenades of higher quality have that stickyness. I do not recall atm if there's a proximity activated explosive now though. But I could see that those GASH grenades would be very cool for that.
Perhaps explosives should be able to be crafted with either which perk from the rare rarity unwards.
Being able to pick up the laser mines and reuse them would be pretty cool