There were two main things which made Starcraft 2 a much more accessible game than Starcraft 1:
1) the ability to select many more units - No problem for Glest
2) The way it handles queuing commands more multiple units - Not so much...
So what i'm suggesting is each command having a tag which determines what happens when a multiple selection is given a command. For example, asking a group of summoners to move to a location should mean they ALL move. But supposing this group of summoners is asked to summon a daemon, maybe the user would click one time for every daemon he/she wants summoned, so the tag in the command parameter would have a different value. This would be especially useful in combat situations, when, if you have say a group of healers selected, they would cast their healing spells one at a time per unit clicked on rather than all just healing one unit. This probabely isn't a problem if you have 300 APM, but for the rest of us i think this could be a really useful feature
I'm unfamilier with the engine, so i have no idea how hard this is to make, hopefully it won't involve too much restructuring
thanks