The original HOMM was a very simple game. HOMM2 was released one year later, after learning what worked and what didn't in the original game. Then, after three more years of work HOMM3 perfected those game mechanics. That's how HOMM3 ended up in a local maximum.

If you want to make a game that's better than HOMM3 in some meaningful ways I think you have to start with a much simpler game that shares some of the game mechanics. That means taking features out. Then you build on top of that to take the game in a different direction. If you take HOMM3 as a starting point you end up adding the features that were intentionally left out 25 years ago.