Sorry, I've been trying to do a post on this once a week but last couple of weeks were overtime weeks. I go to school and work 10 hour shifts Mon-Thur but the past couple of weeks was an extra shift on Friday. So here you go something simple to come up with.
Okay so since this faction was already mentioned in the Crystaline entity Crisis it is a safe assumption that one of the expansions would be Tholians. So this is more like a guess of what the developers have in mind for the tholians and their diamond shaped webspinning ships. Although it is hard to find source material for the Tholians, thye appeared in one TOS episode, were mentioned in DS9 for having a non-agression pact with the dominion, and Enterprise did something with the mirror universe against the Tholians.
Advantages and Disadvantages:
Well for Advantage we know tholians like to be around temporal phenomina so I would say allowing them to gain production from Stellar Phenomina would help them out. Maybe a way they could build stations in stellar phenomina.
Disadvantage is a little tricky as they are discribed as insular race. SO I am thinking never add ascendancy to hegemony attempts (they would rather force the current occupants off the planet they want to colonize) and gain 1 less production in a trade agreement (which could result in 0 trade)
Starting tech. Well we could add Web which would be sort of like a wall. Ships cannot move pass a web toke (warp or impulse) So ships that want to move through web would have to stop on the sector that has the web first then the next move they can move out of the web.
Fleets: Well deep space construction fleet sounds like one. 3 ships and you can remove 1 ship and disband this fleet to immediately build 1 space station. Another fleet idea is intruder containment fleet. 3-6 ships. You may prevent 1 ship from retreating.