Isn't "exploiting game mechanics" just a fancy word for "playing"?
The Dawn of War argument is kinda poor, you still take over control points to gather resources, it's just built a different way. Direct resource gathering is fun because it makes the game harder to play; you have to worry about more stuff than you have to worry about with the other variant. It's two completely different kinds of gameplay, with completely different skills needed to excel. I guess the best thing would be to do the same thing as Age Of Mythology did, where you could choose to fight over plenty vaults, or if you wanted to mine gold/gather food etc. the usual way.
And why shouldn't SCVs be able to fight? What is the problem with stacking a builder unit in an opening so the enemy has to chop it's way through it? It seems like a completely natural move to me. Somebody is shooting you, but there's someone between you and them, so you have to hack your way through the obstruction before you can kill the people shooting you. Can't see the problem at all. Everything that's a part of the game is a valid tactic. Exploiting bugs isn't, but that would be more like clicking special keys to teleport zerglings into the enemy base, not moving units around.
Bluhrg, reedited this post a bit too much, a stupid discussion to be having. Somebody likes one thing, others like the other. The fact that Dawn Of War didn't turn into such a massive multiplayer thing as Starcraft just means that more people preferred the traditional gathering. I guess.