OP stated the requirements I quoted above, AMS definitely doesn't make sense, and I don't think Bambu makes sense either.
Before Bambu, Prusa was the 'no tinker just print' brand, though I haven't used one I agree Bambu's taken the lead now, but I think given OP's desire for more openness and repairability etc. Prusa makes more sense.
Fwiw: I have a Prusa Mini, and I'd buy Bambu today, I'm continually tempted by an enclosed model with AMS. But I'm not OP, and I don't think that's right for them with their description.
An AMS is useful just so you can have 4 different filaments ready to go at any time. Doesn't need to be for multi material models. I have an A1 with the AMS lite and a Prusa mk3s, and manually changing materials is a chore.
Fair point, I don't print enough (nevermind change material often enough) that it's such a bother that I thought of it. I expected the argument to be keeping it dry, to which I'd have said a drybox and/or dehumidifier is better and (could be) cheaper.