Because I cannot watch TNA, I don't really know about the guys that aren't pulling their weight and are useless to the company, but I have an idea of who should be there.
There are a boatload of WWE wrestlers who deserve to be able to showcase their true talents, and the place that will let them do it is definitely TNA.
Chris Benoit - Wasting away his career in the WWE at the moment, or whatever is left of it. He could have so many high profile feuds and awesome matches in a company that doesn't limit the moveset that their wrestlers can show and a company who's fans respect wrestling that Benoit can produce if given the right oppurtunity. The way he is being shown in the WWE is frustrating not just for him, but for fans of Benoit's technical wrestling ability. He has matches left in him, but they will go wasted if he doesn't go to TNA, and I am sure that he knows that as well.
Rob Van Dam is another one that TNA must be anxious to sign. He could intensify the X Division if he is put in there and would be a great buy for TNA. Backstage 'issues' may be a factor in him not signing, but there is too much talent going unused here, and a move to TNA, which is looking imminent now, could really reinvigorate his falling career and be awesome for TNA in regards to the matches he could hold against some other high flyers.
Rey Mysterio - This one is so obvious it is not funny. The guy looks inbelievably out of place against guys twice as slow as he is. He deserves to be put in a division where he can go against guys who can go against him. The Cruiserweight Division is dead, so the X-Division is calling for Rey, unless he wants to be forced to lower his moveset a league below what he showed in ECW and the other wrestling companies that shaped his career.
And lastly Chris Jericho, who would be the best signing they could hope to get. This guy is one that looks to have a lot left in his career and could do wonders for the company. He could bring so much charisma to TNA and he would do great against some TNA talent. Otherwise, John Cena will continue to squash him until his career is officially destroyed.
There are some women who could really build their division. These are not reality though but could you imagine Jazz, Trish Stratus, Lita, Victoria and Jacqueline or another high quality woman wrestler going around in the TNA women's division? If they are ever going to have a credible division, those are the sorts of women that would help them do it.
There are a lot of people who deserve to be in TNA and are being wasted with what they are doing now, but what they should be doing is focusing on developing young talent to build up to main event wrestlers.