Don't forget to increase the location limit significantly. Either that or implement a way to recycle locations. (Custom locations and trigger location repurposing)
Everything should be implementable unless someone starts modifying every version of the old maps and breaking them on purpose. Simply don't modify, just add on top. It's always easier that way.
Make easier kill for money conditions, death counters/integers, unit spawning, unit detecting, mobile grids, walking detection, unit switching, vehicle loading, special effects(unit deaths), computer unit orders(ex We Are Friends), death detection, hallucination distinction from real units, etc.
Overall easier and more natural please, that's what killed SC2 ums map making along with the crappy game lobby and no ability to: host, save maps and appear at the top list.
Other points of interest for the editor are:
Off-map UI. You know how you always have to waste space and triggers for tech buildings, spells, items, inventories. Then you have to keep the player from glitching it and lifting the barracks like a retard or unburrowing an unit.
Custom map size and short-distance map rendering.
Let's say I want to make an RPG, but I don't want to pre-render every 256x256 and I simply hate having to fill up every corner of the map with something and keep track of my map's space. So a 2560x2560 map which just renders 64x64 at a time would be useful, especially when we're talking 1 grounded hero unit per player. I don't mind working in squares and rectangles, when I can just build islands and just wall off everything and create my own octopus map, but it's a waste of space.
The option to give vision or ally/unally at a specific location. Ability to unally specific units. The option to finally unburrow/cloak all my units at once. (Very, very useful in a lot of cases.)
Hold position should no longer slow down your attack speed compared to letting your unit move freely.
AI doesn't give up so easily or stops following you the whole map like an idiot. Medics stop trying to heal a unit at the other edge of the map.
Better options for spells/abilities/cost conditions. We had build a unit and drop a unit. Optimization for the Bring trigger will be useful.
More options for dodging chance, so far we only have prottoss shields, trees, cliffs, invicibility triggers for attempting an RNG evasion chance. Let's say I want a good undecided swordfight between zealots. Perhaps making the auto attack slower on purpose for specific maps.
Faster/slow loading for transports. Larger transport cargo/less cargo size for big units, the ability to give any unit transport abilities and anything more advanced in terms of unit storage.
More options for detecting type of terrain. (especially useful for zerg creep, a lot of people had ideas for creep, but it's not interactive)
Differing units. No more having to be restrained by the limited number of SC units and then painstakingly upgrade every unit to offer end-game enemies. (Which cannot be downgraded, you can't directly order the computer to upgrade and there is no trigger for upgrading, then there's the +1 armor problem, when attack can give +100dmg per upgrade) Would be really great for balancing rpgs, when the players are either too weak or too strong.
Being able for melee units to attack air units. This was a major pain and made corsairs and devourers useless even in ladder maps. Same for Ultralisks compared to Archons.
None.
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