I don't think I'm OK with tacking on phase engines to stabilize phase space. They seem like two totally different techs, and I really don't see the point of colony pods, especially with VR. I also think 3 upgrade slots it kind of high, but I'd be OK with it taking up two slots.
I would be ok with maybe making the upgrade slot cost fleet supply (between 20-40), but I don't like the idea of cap ship slots.
As for unlimited number as Sareth mentioned, I don't think the problem is UNLIMITED as it is that you can jump out a badly damaged SB and jump in a brand new one. Let's face it, you only have so many fronts to defend. I think something like a 5 minute cooldown for the "ability" might in order (and somehow tie it to preventing additional jump ins if the first blows up). Perhaps even add AM as a prerequisite to jump, so you might have a fighting chance of preventing it from jumping (disc AM steal or dunov EMP).
Right now we can spam unlimited numbers of these up to the point that you run out of gravity wells and/or the hardware can't support it.
20-40 logistics slot requirements is quite a tame number indeed, and isn't more then a capital ship. It should be at a miniumum 100% more logistics slots compared to a cap ship(coming to 100), as the relative power of a vasari starbase is far greater then that of even 2 cap ships, or even a lvl 1 titan. The starbase can be very strong, and it has many abilities that can be upgraded into it, and it can clear out dug in enemy worlds, Like a titan. It just levels differently(economically) and when fully upgraded its as strong as a levelled titan. It should require at least one capital ship crew to help create a hard cap on the absolute number of these that a vasari rebel player can be able to field in the game. Requiring capital ship crews would also increase the cost of spamming these pseudo titans.
If your team has 5 of these in a 5v5, then they have 5 more titans.
More titans means your team will win, as 2 titans beat 1 titan. Its really quite simple, and needs an obvious nerf in both the efficacy of vasari starbases and in the amount that these can be spammed.
So for the cost of one constructor, one starbase construction cost, and one starbase upgrade, you will have a starbase capable of walking through the enemy worlds, which can be upgraded as the tactical situation permits. Imagine how many of these you could spam creating wave after wave of these monsters. Getting a kostura cannon up and running only exacerbates the imbalance, as you now can send a starbase anywhere in the map anytime you wish.
These unupgraded vasari starbase are effective enough lure to prompt a strong defensive action from an opponent and be used to lure away enemy fleets, giving the vasari rebel player near total control of the most important aspects of the entire match. As howthe has also said, they are easily retreated from a fight at low health as well, and all you need is a friendly cross map phase node to retreat them to. No losses, while the vasari rebel starbases are killing entire fleets and slowly choking all worlds with their starbase spam so there is nowhere to go. This is a hard opponent to 3v1, let alone 1v1.
Its simply intolerable.