Would the FWL, with all its ties to ComStar, be willing to commit troops to help protect Terra in this scenario?
Depending on what Waterly can offer Thomas at that point. After all Hanse had to literally "threaten" his child just so the League begins production of the upgrade packages as quick as possible. What can Comstar offer him? Threatening with his real identity which at that point only a few within Comstar knew?
For a trap at Terra: Could Comstar reactivate the SDS facilities in time? Terra still had several but all were mothballed (including the surviving Castle Brians). The fleet was at this point I think at least partially active so at the least there could be one naval battle over Terra. Though of course the Clans could also activate more ships by simply pointing the Snow Ravens at Terra (the Ravens were already working in an auxilliary role). Other then that: in the novel where focht bargains with Ulric he mentions that Comstar will use every force at their disposal except the two Terran divisions (the bodyguard of the Prima). So at the very least Comstar would have at least one Mech regiment and some other units left but that would never be enough to even put a dent on the Clan's ground forces