Apples and oranges. The founders pack was a unique situation. And they also were never available to F2P players, while the Mk1 weapons have always been available to f2p.
THAT is my biggest complaint. I have all the mk1 weapons beefed up with everything, including the incarnon adapter on my mk1 furis. And the complaint isn't "I'm losing the stance forma's, 20+ regular formas, arcane adapters, incarnon adapters, orokin reactors", it's also that I'm losing weapons that I enjoyed building up and continue to use. For the longest while I had a dedicated arsenal loadout that was excal, and all the mk1 weapons and taxon, default colors, default skin, no fashionframing at all. I'd use that loadout for sorties because I found it fun. Everybody else going in with their meta gear, number crunched mod configs, ect... and me with the newbie gear looking like I just finished vor's prize...
I can understand DE wanting to streamline things, and overall no, not every player's gonna be like me and keep every single weapon. But it still doesn't sit right with me.
I do hope that when they remove them, they refund the resources spent.
I also hope they adjust the build costs for a couple of the non-MR locked weapons to be credit purchase only for new players. Having 1 weapon of every basic weapon type available to build for just credits allowed brand new players access to them to get a feel for how a shotgun plays vs an assault rifle vs a bow, ect, WITHOUT having to invest material resources they do not have being mr0 literally just out of the tutorial. The Lex is, as far as I recall, the only non MK1 weapon that is credits only, no bp+ resources. Yeah, I know, the resources needed to build the baby weapons is nothing.... for anyone mr1 or higher. But again... brand new players, literally the newest of "new player"...