quite honestly, I was hoping for something along the lines of 'forking the network', to which I could trivially suggest setting up a defederated instance or somesuch. all the changes you have in mind sound like plenty of work, that might be done either on apps or servers, and it's not even clear that mastodon would be the best starting point, but surely it wouldn't hurt to file feature requests in mastodon's project, especially if there are plans to contribute implementations for them. I haven't giving the features proper much thought, and I only interact with mastodon users indirectly, so I know very little about it myself. good luck!