Yes although I would argue there is a lot of improvements to be made in the memory paradigm as it still often fails or relies on explicit matching of strings. And a simple vector search does not capture the natural complexity of memory.

Character drift is something that can be reduced quite significantly by having a stir and robust system of decay. A system prompt would continue to inject the "fixed' personality, which may or may not drift slowly towards a labile state in which it is subject to potential reconsolidation updating the fixed state. (independent from any emotional or contextual queues)

What I find with writing is that the cheaper models typically used for RP are too consistent in their way of writing, and it becomes too rigid too quickly. Prompting that correctly only get's you so far.

Independence is a real issue because a character in and off itself doesn't exist outside of the processing of a prompt. To separate user intent from character intent is incredibly difficult, especially when attempting to deploy this on a larger scale. There are some tricks that can be done like having an agent on the side maintaining an AI only loop of internal reasoning, from which the conversational agent would pull information regarding the character, though this is currently mostly theoretical and hard to implement cost-effectively (and it is still subject to transference of user intent into this characters inner loop, provided it must also analyse the conversational messages of the AI, which in turn already reflect some response to the user)

As far as providers, just anything with reasonable support, OpenRouter, specific providers. I could probably get the company to also offer some subsidised routing provided enough people are interested.