Here's Claxton and Q's stats this season, compared.

If you look at their per-36 it's not that big a difference...Claxton is a slightly better passer, Q is a better rebounder. Neither space the floor, both suck from the FT line, Q has a better net rating but that's probably because he plays with better players than Claxton. Defensively he's more mobile than Q so you don't have to play drop cover as much. So there's an argument that Claxton would be better if he played with the Cs, doing what Q does. And since you're not trading one for the other, you're basically just a slightly better Q for the cost of Simons and a first so you're helping your depth stocks. If Q is injured, you have your other Q. You don't have to rely on Garza or X or go small ball.
It makes sense until you consider the salary cap impact. Q is on a 2 year contract at $2m. Claxton is on $25m a year give or take till 2028-29. It's a deal that washes out from a Cs cap point of view, but it's the opportunity cost of what else you could get back with that $27m, because so you're adding another Q (call him a 120% Q) for 12x the cost plus a first.
If your goal is to get a tradeable contract on the books, it would be better to trade Simons to fetch 2 or more players to break up his $27m. Claxton is probably tradeable at 25m, the fact you're considering it shows you feel he is worth what he is getting paid. I'm just wondering if that's the best deal out there for Simons.
As for whether it makes us a contender, what I see is it adds to our depth by having another player at the same level as our current starter, so we have insurance in that position, albeit at a much higher cost.