Your ideas are cool, especially the first one. I think S5 would be better for Tamaran, though.

For me, I'd wanna see Gar and Rachel stay together in S4. They work well together and have been learning together. They spent all of S3 apart and the show kind of suffered for it (Gar spent the first few episodes having conversations with himself because Raven wasn't around). I liked Connor and Blackfire as a pair, and think they'll do well again together, but I want them apart for a bit while she builds her reign back home.

Ideally, S4 will train Rachel and Gar to be more confident in their powers and building their relationships with others. Kory and Dick will be forced to reconsider their commitment to supporting the two younger titans through their own ambitions and conflict (this is what leads to Kory returning to Tamaran at the season's end). Connor takes the role of lead next season and makes very morally ambiguous decisions to save the Earth from a threat that's human made, not superhuman (working mainly on his own and with other superheroes outside the main four, such as Donna and Dawn and ARGUS) and eventually flees Earth out of shame. Dick and Donna seek him out and end up on Tamaran with Kory, leaving Dawn to navigate the ever increasing powers of Raven and Gar on Earth in S5. Jason gets one episode where Dawn, Connor and Donna fight over what to do with him, resulting in his incarceration. Dawn finds out Dick forgave Jason without penance and her indignation fuels Connor's darker side, Donna tries to remain just.

I'd like Lady Vic and Rose to come back. I really don't want to see Tim Drake back and Bruce Wayne can stay gone for the foreseeable.