Problem #1 You have no idea where your nearest opponent is at the start of the game. Spawn near an FE, good luck with your Strat.
Problem #2 Even with a 40% fire rate, 20 corvettes is going to do pretty poorly against early game starbases. Not to mention any corvettes the opponent also happens to have in system to support it.
Problem #3 Where are you going to get all the influence you need to actually claim their capital system so you can take their pops off world? Even with a clustered start, that's a still a hefty tag, and the moment you do it, a human player, at least, will start to build up their military. I suppose you can get around this by going purifiers, but then you've already thrown your cards on the table.
Problem #4 Armies? You need armies to take their worlds. Even if you take the system, starting defense armies are pretty tough. Sure, you can sit there and bombard all day, but 20 corvettes is going to take a looooooooooooong time. (Even longer considering you won't have 20 by then)
Problem #5 Seriously? Your going to turn off tech? You do know gun upgrades are commonly one of the first techs offered, right? Better hope your opponent isn't researching one before you decide to storm them.
Problem #6 Multiplayer. Where exploiting kills SP depth of gameplay.