I think something cool to add to franchise mode would be players' primary positions changing based on how many innings they play at a certain position. Like, if I play a primary CF in LF for the season, LF would now be the primary because that is where the majority of the season was played. This feature could also include adding secondary positions. Say I play someone who is only listed at SS at 3B for a certain amount of innings, 3B would become a secondary position. It would kind of be like this player is learning a new position, where the more they play there, the more comfortable they get, and the better defence they will play there. I think this could also work for pitchers, where if they reach a certain amount of starts in a season, they will be a SP. Same sort of thing for a RP, but this time it's a certain amount of bullpen outings. I also think that the stamina attribute should reflect a pitcher's recent workload. Say a SP is moved to the bullpen, and has been throwing in a few short outings, maybe 1-2 innings each. Instead of the stamina staying in the 60-70 range, it would fall to the 30s. This could also make it feel like when you are stretching out a RP into a SP, you are actually stretching out a RP into a SP, making it more realistic (instead of bumping up the attribute manually). I don't know how hard these would be to add to the game, but there is a similar system already, with the two-way status thing. Regardless, I think that the mode will feel much more realistic with these features, so, yeah.
I would also like to see actual broadcasters in the game, like FOX, TNT/TBS, MLB Network, Sportsnet, etc. I do not know what the cost for those rights would be, but hopefully it is cheap enough for SDS to make some deals and include in The Show 27. It would be really cool.