Hangman vs. Takeshita and Fenix vs. KoR could both be top-level TV matches if given the right amount of time. Takeshita is sticking around for a year so I expect him to get a really good showing. Darby vs. Cole should also be really good. I have a sneaking suspicion Cole vs. KoR could be the tournament final with KoR winning it.
As for the jokers, Athena is from Texas so is a very good chance especially given the dearth of big name female free agents. Taya Valkyrie is another option, she's back working IMPACT but non-contracted I believe.
The male free agent could be one of many. Claudio 'Cesaro' Castagnoli is the first name as he and Joe faced off in ROH and WWE, and could have a very physical match together.
But there are a ton of free agents or non-exclusive talents out there such as JONAH (Bronson Reed), Harry Smith (Hart family connection), Tom Lawlor, Josh Barnett, James Storm, John Morrison and Johnny Gargano. I feel like JONAH would be an interesting choice since physically he is similar to Joe. New Japan's Super Jr. tour will have kicked off next week, but a lot of the heavyweights don't work those shows, so a NJPW guy isn't impossible (but I'd be saving them for Forbidden Door).