I have read the arguments, but disagree. It is time to upgrade the base set keg. This keg has been around for 3 years, most of the cards in it have been power crept out of the meta, and most of the existing player base has a full playable set of base cards.
I have the full set of all cards now, and you have to craft and transmute quite a number of base set cards to do so. I had 53 legendaries to craft, 37 from the base set when i finally broke down and gave up trying to pull them from packs.
I love pulling cards from packs, it was my first job in the 80s when i worked in a card and comic shop. I learned then that every chase card was not shipped to every region of the country, to promote collectiblity. The passage of time has only enforced that basic tenet. most games, Gwent included, have algorithms that will not let you pull every card just from packs (or whatever other randomizer they use.)
So if having a keg dedicated to the base set does not help you pull the last remaining cards from the base set, might as well open it to all sets. At least that way, some cards from future sets are guaranteed.
Take a random numbers generator and program it between 1 and 200 (not actual numbers just using basic numbers to illustrate my point.) Add 200 more so now it goes between 1-400. Now aim for the numbers between 50-60. You tell me, where you better off before or after you added 201-400?