Well, the classic Risk works quite well without different unit types. And it's one of the best board games of all times so it can't be THAT wrong....

But I agree that you would have to adjust some systems for that in order to integrate the new "simplistic" version into the rest of the game. But perhaps it would be worth a try on the green field, just to explore the possiblites and possible flaws and benefits.
At least there is one simple reason when designing anything: make it as simplistic as possible and only add complexity when it's needed. A simple system that works well is superior to a complex system that has its problems..... wink
The geek would disagree that Risk is one of the best board games of all time...
http://boardgamegeek.com/boardgame/181/riskBeyond that though I'd agree with you that it would be an idea worth considering and experimenting with, except that we're 6 days from release and going back to the fundamentals isn't really an option.
With the system as it stands you've got a lot of interesting decisions in what units to build on the campaign map. Troopers are cheap and effective, Hunters are fast and enable you to capture a lot of ground quickly. Shaman can preserve your forces so you don't lose so many in advantageous battles, Transports and bombers help you plan ambushes, Warlocks can effectively counter these manoeuvres.
It would take a lot of work redesigning the systems in such a way you still had a lot of interesting decisions. At this stage I think Larian are closer to fixing the existing system than would warrant stripping things out to that degree. In practical terms it's an impossibility anyway. If you were talking about Dragon Commander 2 I think it would have more merit.
Oh and I'm typically playing vs AI, my dexterity is nowhere near the level that I could play an RTS online and I wouldn't be able to fit in a whole campaign anyway.