So far I've only played the map in single player, so that probably informs a few of my suggestions. Either way, here we go:
1. I know I'm not the first to ask this, and it is probably quite a big ask, but a dedicated single player mode would be great! The most obvious ideas are tweeking enemy difficulty, in particular some of the bosses, or allowing for multiple heroes to be selected.
2. I would love to see a recipe vendor both at the starting location and the "hub" area with the teleporter, the other vendors and the forging dryad. In the beginning it would be great for new players to plan their items ahead of time, and in the hub it simply seems a hassle having to run to the next proper vendor from the teleporter, when almost all other shopping can be done right there. Likewise, a resurrection stone in that area would be great. There is one not to far from there in the Garden area, but it seems a bit arbitrary not to have one right at the most "central" spot.
3. I found it quite annoying having to juggle all manner of items in the relatively small inventory, especially quest items, and keys. Maybe there could be a dedicated inventory for quest items, or acquiring the items could set a flag, so the item doesn't actually have to be in the inventory. I have no idea how feasible that is, and how either solution would impact the process of using items in various spots though. A particular offender in this regard was the Moon Key. It would also be helpful if some quest items could stack (Gate Keys, Chest Keys, Explosives), and others had a fixed and visible amount of uses and would disappear after they were expended (Moon Key, Eilric's (?) Key).
4. It is quite annoying that only one telelporter destination can be active at one time. This makes backtracking for quests quite tedious. Of course I understand reworking this system would be a big ask, but maybe the central teleporter could bring one to a sort of hub, with different teleporters marked for their destinations.
5. A minor thing regarding teleporters: I could not use them with non-hero units. I don't know if this is intentional, but it would be just that little bit neater if that worked too. In the base game there are gateways that can be used by all units, I don't know how all of this works, but maybe they could be used for this sort of thing?
6. The "stats"-system is a great way to customize one's hero, but is it necessary to access the menu with the Esc-key? I am very used to using Esc to exit submenus, and I found myself in the stats-menu at some very inopportune times because of this. Couldn't it be made to work similarly to the Talents- and Glyphs- systems? Also, it would be great if one could reallocate stats like those two systems!
7. I would love a commandline that returns the hero's current attack speed! In particular when building my Hunter, I wasn't quite sure when I was at maximum speed, until I had solidly overshot the mark. In conjunction with this, I would love a more in-depth explanation of how attack speed works in the help menu. I assumed that the increase in attack speed was calculated something like (sum of attack speed bonuses from items + agility * 0.5%), with the cap being 100%, or double the base attack speed. I was however unclear on how temporary effects interacted with that. Can they break the 100% limit (it looked like it), or are they subject to it. The ingame assessment of a unit's attack speed is woefully inadequate to judge these differences.
8. Lastly, I would love to be able to disable instant death traps after they are cleared for the first time. There is one example with the towers that are destroyed by entering a circle of power they guard, but the many "minefield"-like traps and moving platforms over spike pits were very annoying! Especially when I tried to move non-hero units while paying closer attention to my hero!
Thanks for an otherwise amazing map, I am really impressed with what is possible in WC3!