Developers have to play all previous HoMM games with all addons (including Heroes Chronicles and WoG) - maybe then they understood what new HoMM needs. Oh, and use all map editors too.
1. King of the hill - all AI players against human - and should be different then alliances.
2. Choose AI player difficult and I mean for each player separete - not only general easy/medium/hard.
3. Artifacts guarded by neutral creatures (like in H2) or pickable only if hero have some skills.
4. Caravans should be from beginning.
5. Flagable windmills, watermills, magic gardens etc. It's not fun to vistit them weekly.
6. Campain like in H2 - when you can choose and betray sites and also have to choose what mission is important - like help allies or slay enemies.
7. Lots of game map - not only few like in H5. And return of map desing like "Broken Alliance" from H2. And it would be nice to see one map which is continent /land of new HoMM game (something like Enroth map in H2).
8. Return of heroes advanced classes - maybe not so much like in HIV. And also return of might and magic heroes in each castle.
9. Spells - for singleplayer return of good, old Town Portal and Dimension Door. Also I think we have magic schools only avaible for certain races/classes.
And more spells then in HV - even if some will be used once-two times in game.
10. Skill/stats system - get rid of this system from previous games where skills and stats were fix at map start. So if I for example save game before hero level up and next load game - I will have different skill to choose. It can be unbalanced in singleplayer but choosing skills and abilities in H5 was a pain - building your here only to be screwed out with one bad luck level up skill choice.
11. General options for turn on/off depending if we playing single or multiplayer game - example power of Town Portal (all cities/nearest city).
I think in case of multiplayer we also should have some options to ban certain artifacts/spells/monsters/heroes/etc.
12. Neutral creature dwellings - for all neutrals even for the most powerful. Also their guards should increase with each weak for certain % (however lower then neutral stacks %).
13. Different spell formulas for heroes and creatures. So high level mage can defeat enemies with his spells not just with uber-army.
14. Return of ghost from H1-2 and hunted/elemental guarded mines.
15. Return of Ultimate Artifacts and maybe drop of Graal. HIV have IMO the best digging artifacts system.
16. Different playing style for each nation - like in HV where barbarians have rage and were completely different from other races.
17. Only some creatures should have upgrades - but two (alternatives like in HV). And no re-training from one alt to another - you have to choose upgrade wise.
18. And enought
of bad spelling.
1. Each city with unique desing - not just central pillar and building around it. Look at HoMM2-3 - different city - different building places.
And it would be nice if town ground - maybe even sky - will be deppended on map terrian (like in HIV).
2. Different models for male/female/another race heroes. On map too. How long we have too look on female wizards with beard in Heroes games?
3. Life in cities - add some citizents there - like in H1 or on HV game installation screens.
4. Different battleground desing when we fight in creature banks. So they not look the same like terrian battleground.
5. Back to functional user interface - not just as minimal as you need to play game. And no more lack of "wait button" or other shortcuts. Everything should has access from UI too.
New features (from other games):
1. Add one more map level - maybe sky plains or undersee? Not a must be but would be nice.
2. Heroespedia - maybe remember Dune II (not mention about Civilization or X-COM) where you have button with access to units and buildings description (and short story about them)?
3. I will be plaesed to see terrian changes as in Disciples but it is not must be.
4. Paying for army maintance (once per week?) - so player have to choose - larger but weaker army (low levels creatures) or lesser but power army (high levels). And peasants with their tax income will be more important then. Oh, mages should pay more for army then knights - after all they should have powerful spells to help them.
5. If heroes stays in once place (or sleep there) for few turns, he should have some bonus to defence in battle.
And two more thing:
1. Hire someone who canl write at least decent storyline and dialogs.
2. Give manual which would not be few pages short and will have in it game mechanisms described. Just look on Ubisoft HV manual and Fan Manual. See the difference?
It would be nice if manual have some in-game story - like in H1 for example (Letters of Morglin Ironfist). Map where new game take place also would be nice.