While I fully understand the logic behind the reset, and agree that it is generally a good thing for Extraction games, I think Faction Upgrades feel like they should be permanent. They way you unlock them so slowly over the course of a season and can never actually lose them apart from the season wipe just seems to cause them to slot into the part of your brain that assumes they are permanent.
I propose a compromise:
A ~50% (more or less, so long as it is a sizable discount) salvage discount to repurchase any upgrade you bought in the previous season. So what you upgrade in Season 1 will be discounted in season 2, what you upgrade in season 2 will be discounted in season 3, ect. If an upgrade is discounted, but you don't buy it, next season it's back to full price.
This way the grind is lessened for people who actually managed to max their upgrades, while also allowing those with less free time to slowly climb higher than before, or allowing your chosen 'must-have' upgrades to be quick while giving you time and spare salvage to experiment with other upgrades you otherwise wouldn't bother buying. It still wipes each season, but this way there's just a bit more slack for toying with different builds without feeling like you're missing out or need to grind excessively.
It will also reduce player friction, because I strongly believe this will be a major pain point that will be complained about a lot come season 2, and I think this would be a way to preserve the core concept of the seasonal gameloop while also smoothing out a bit of that friction it would otherwise cause players new to the genre.