There are problems with Company of Heroes GUI being used since Megaglest is pretty sandbox in comparison. In Megaglest, you can build production facilities anywhere on the map and this may cause rally issues. Units may enter hostile territory by accident due to the placement of these facilities. Company of Heroes is simply a different sub-genre of RTS than Starcraft, 0 A.D., and Megaglest(at least in my opinion, because the Starcraft is all about build, produce, kill with a sandbox like approach).
I've been playing Glest/MG for years now, and I still find new hotkeys that I never knew about. This isn't great interface design, and is one of the top complaints about older versions of Blender.
The only way to discover hotkeys is through trials and error and curiosity. Why? Because the issue with hotkeys is that it isn't taught in Megaglest. There are no tutorials, explanations nor campaigns that teach anything, which is a serious problem in itself. People have asked me how do I produce that many units or how do you get an army so fast. It's because I have brought experience from other RTS games which have explained their GUI, so the player base would be more evenly matched and informed. Therefore, I find that a GUI based on hotkeys is necessary, since it evens the playing field and optimizes gameplay.
But how do we teach them? Easy.
Make Mini-Campaigns of 5 missions that teach the players the basics. To prepare the player for PvP, the player should be required to finish at least 3 missions of the campaign. Those 3 missions will teach the players all the basic. The rest of the campaign will teach the player advance tactics, if they are interested.
Add more tips in loading screens. Having 3 tips that teaches the player important hotkeys or tactics will help players remember the hotkeys.
These methods will make hotkey and perhaps future features easier to remember for the Steam Playerbase.