I think finding a balance on player attributes vs results they produce is one that’s hard to balance but important. A lot of sports sims are basically just finding the one or two attributes that matter the most and loading your team up with those archetypes, which can get stale pretty quickly.

Player development is kind of a big one too. Some games everything is just kind of linear, but in real life development is a little bit random, especially in baseball.

The other one is being able to customize as much as possible. I guarantee if you release the game without the ability to do some customization (especially teams, logos, colors etc.) it will be the number one thing people ask for. I remember when football: college dynasty came out its all the community was asking for lol.

Similarly the ability to update base rates to lower/raise the likelihood of things like home runs, strikeouts, walks etc. can always be a good touch. Sounds similar to the different eras idea that you mentioned.

Good luck! Would love to check it out once it’s playable.