BookBarbarian
Expert Long Rester
a now, more-or-less, "ex-5e DM" at this point
i'm sorry to see this. While I personally have no problem playing a Featless PHB game, heck I'd even play a Basic rules game and I don't even mean all the stuff that's in the SRD literally the original 5e basic rules where the only classes are Champion, Thief, Life Cleric, and Evocation Wizard.
But in the 5e game I run I allow anything from WotC, UA, and 3rd party. as long as I review it before, and am open to tweak it as we go. I've found it works fine to just let try and play what they want, and adjust as we go.
That said, I have recently switched from 5e to Adventures in Middle Earth. Only six classes and no 5e spellcasting system was a pretty drastic change. It's been really fun as a simple "5e" game.