People like 20 minute rounds? Oh they must be all the screaming 12 year olds spamming GOGOGOGOGO in most RTS's I have played. I prefer longer matches, like those found in Supreme Commander when I played it. Games like CnC3 where you just spam units till one side collapses after 10mins is just boring. The lesser the time a match takes, the harder it is to make a come back.
Games of SupCom vanilla, when I played online, also completeed in under 30 minutes most of the time. Turtling wasn't an option if your opponent harassed you properly and took the rest of the map, and it was mostly decided by the end of T1 who was going to win.
If your games were taking an hour your computer was either at -10 sim or you were playing at a low skill level.
Your generalisation of people liking half hour games to 12 year olds is amusing...funny how there is little to no demand for multiplayer games that take an hour or so isn't it? Maybe that's because it's not just the 12 year olds who like half hour sessions.
I don't play CnC3, and have no interest in it, but I'm guessing Starcraft is another one of these games where you just "spam units." Here's a thought: 99% of Supcom units don't have abilities, so all you do all game is spam units. Compare this to Starcraft, Warcraft, Dawn of War, Company of Heroes etc. where you need to activate abilities very quickly and on a large number of units, and you'll see that it's actually the SupCom/TA model that is about spamming units.
I'm going to say that DG is about your hero, and playing against your opponent's heroes, and towers should not be a major factor in this relationship. If your opponent is capping your flags, it is YOU that should be doing something about it, not your towers. If the opposing team manages to play 2v3 and have a third off capping your shit behind your back, you deserve to be punished for poor play.
I don't want a viable strategy in this game to be "Upgrade towers, sit behind them till we get to lvl 20, buy toys, hit enemy." and that is what you are moving towards with your buff towers ideas. There should be engagements at every stage of the game, and by having towers on normal you facilitate that. Putting towers to high prevents it, ergo it is a worse option. Why don't you just put starting level to 5 if you don't want to play early game...