but your opponent has the same Problem. So may the better tactic win...
NO. The defender does NOT have the same problem, because he has a fire spitting dragon ready in the gravwell, while the attacker has a jarun migrator that can suck its tentacles at best. About two* minutes later that migrator, should the attacker have a dozen overseers healing the starbase as it is constructed, will become an awesome 3k HP, 149 pulse cannon damage death star. Great! During those two* minutes the defender has a 12k HP, 350+ damage monster spitting molten fury on that toy that the attacker has just finished constructing. On that toy and on everything else that came along.
The *advantage* that TEC have above Vasari when assaulting a Vasari player are the Torpedo Cruisers. YES! They ARE an advantage, because they can start pounding on the Vasari starbase from the very first moment they exit the phase lane. They are ready to fight, unlike the Vas starbase. And the defender's Orkulus will make short work of anything unprepared for it, wherever it may be in the gravwell.
What makes the Vasari Starbase a viable counter to other starbases (being buildable some distance away to fly in and kill when it's ready) becomes its biggest disadvantage against another Vasari Starbase, simply because it cannot do ANY harm to it for the first two* minutes and is only a far weaker copy of its target in the battle ahead.
Back to Kostura for a minute.
Now that I hear Kostura doesn't turn off the defending Orkulus for any sensible period of time, I think it is not a big advantage when attacking an entrenched world. Yes, you turn off the tactical structures. Yes you harm the ships a little bit. But you still have to cope with that big flying thing. Fifteen seconds of stun will not win the game for you. It is your fleet against his fleet and his well upgraded starbase. Attacker is at a great disadvantage, as he has no trick he can use that the defender can't use on him, while the defender has a developed starbase.
Ok so we're left with using the Kostura to skip the enemy starbase and jump right into his territory.
Here's a list of things you have to do just to be able to send your fleet into his territory using the Kostura:
+ 8 weapons labs
+ Kostura Research
+ Kostura Construction (8000 credits!)
+ 5 Imperial Labs
+ Phase Stabilizer research
+ Phase stabilizer construction
Ok now you can send your brave fleet into his territory. Bam, jump, wooosh, whatup. You're in the lion's cage.
Your Kostura will reload for 6 minutes. You are most likely NOT going to colonize the planet anytime soon, because YOU ARE IN THE MIDDLE OF HIS TERRITORY = HIS CULTURE OWNZ YOU.
You are also going to have company pretty soon. YOU'RE ATTACKING VASARI, remember? They have phase stabilizers too. Even if you siwftly kill the one in your current gravwell, the enemy still has all of his units at most two jumps away from your little invasion. Also, this is his territory, so he's likely to have a few frigate factories in the surrounding gravwells as well (and if not, what will stop him from building some?).
You have to keep your army in touch for reinforcements, otherwise they are already screwed up. What options do you have?
1) Have a level 6 Marauder ready. Ok. add that to your preparations list. and hope the Marauder doesn't get killed in five seconds when the defender brings his fleet.
2) Quickly build a starbase and equip it with phase stabilizers. In that case add the following to your preparations list:
+ research starbase
+ research starbase phase stabilizers
+ have a migrator ready along with the money you will need for that starbase and its upgrades.
and all of that just to establish a foothold in enemy territory, surrounded by HIS planets, HIS culture, HIS factories.
... if anything, this tactic is viable against Tec or Advent, because they can't use phase stabilizers to swiftly counter your attack. But against Vasari... it's like a suicide.
Compare this please to TEC's invasion strategy:
+ 3 war labs
+ build a bunch of torpedo cruisers (one lvl 3 research?)
+ build some carriers with bombers and garda's for enemy fighters, plus 4-5 hoshikos for repair. (All of that requires only low level research)
+ send that in for carnage.
+ keep sending torpedo cruisers from different angles in packs of 4 so the starbase has to turn around each time.
* - I'm not sure just how long the Vas starbase builds in an enemy gravwell. It isn't fast enough to catch the defender with his pants down, that's for sure.