Having 85 man rosters will help, but it will suck having your heir apparents transfer out. It's real life, but this is a video game. There definitely needs to be sliders/options and a morale system and clear parameters on why a specific recruit would want to transfer. Whether that's being promised a starting spot, bringing in a player has higher overall, number of snaps/stats, quality of team, scheme, etc. There needs to be a coach skill that we can earn to increase the chance of guys to stay.
I was thinking about something like Madden Moments. I think NBA 2k has something similar as well. The only hangup about that is that it's hard to truly start in the offseason without completely changing the landscape of the mode. You can't really start before the winter portal or February recruiting window without all the other rosters being affected. If I start as a HC, i would expect to see a wave of guys transfer out. Then would need a pool of players to choose from. A lot of gray area that needs to be considered.
I'm not sure how to handle that properly. How can you start in offseason with the portal and signing day. Without it changing the opening day roster. Only thing I can think of is there being a small pool of fictional players for you to choose from in the Portal and your players end up on random rosters. If I'm doing a 1 star school dynasty, it would be cool to utilize the Transfer Portal to get Plug and Play starters so that you can start off and be competitive. But, I don't see how we can start off at without the landscape flipping before the first season even starts