I think you make a lot of good points here, but there are some I'd like to voice my dissent/general thoughts on.

1(c) I don't really disagree with this request, I'm mostly highlighting this one to voice my thoughts that I'm not sure if this request is viable alongside the way Larian currently approaches enemy combat design. It feels like they want to make each fight distinctive in a way that would make random encounters not their prefered way of doing things.

2(a) I disagree here mainly because in D&D, DC is meant to represent the difficulty an average person would have to do a particular task. An average lock is always going to be an average difficulty to open for anyone, the deciding factor is how far above or below average the character doing the pickign is. The point of getting bonuses and proficiency for a character is to demonstrate them being good at a thing. Anyone can attempt to break a lock, but rogues have proficiency with that sort of thing because part of being a rogue means being good at it.

It also will make it far harder for a party to do without a rogue or similar class, which given the fact we only get a four character party could lead to players requiring certain characters as necessary on any playthrough. For instance, I play a Ranger who's also good at lock picking and trap springing in part because I like the other characters more than Asterion and want to spend the most time with them. Changing DCs based on class would mean that either I would have to play a rogue (which I am not at all interested in) or I'd have to constantly have Asterion in the party. I think actually changing DCs based on class is a move away from How 5E is meant to work in general. Though I do think that some dice checks probably should be adjusted a bit more.

2(c) I'm curious why you think this should be the case. I personally disagree because, in my opinion, Inspiration is explicitly a tool for when you REALLY want to pass a particular check. It's meant to help you clinch a really important moment or help your character shine doing something you feel like they should be able to do. It feels like it defeats the purpose if using Inspiration just makes a check incrementally harder each time. At the very least it kind of disinsentivises using Inspiration for rolls that are already tough to begin with.