After some more thought on this subject, the main beef I would have with changing the coaching budget to something similar to a scouting budget would be two things.
1. As Bripat referenced above, it dumbs down the game and I'd prefer to be rewarded by doing more work;
2. Right now, with the exception of a great FI, it is mostly unclear how much a top mlb coaching staff actually helps the development of your players. My guess would be that it helps in spring training bumps and keeps older players from declining so quickly in some sort of capacity. If I have to pay $20MM to be sure that this continues to happen, no thank you. I can usually get it done with $9-$10MM or if I need an FI, I can get it done with $9-17MM. Also, with the current system, I don't even know exactly what the coach ratings do for discipline, patience and strategy. I know what the player's guide reads, but we all know that the language used in the player's guide is left vague on an intentional basis. Maybe if there was more transparency on those less known coach ratings, the evaluation would be more fun. I don't know, just a thought.