The idea sounds sick if it's done in the right format. I'm not sure if people want the players from each team to actually play vs each other, or if people just want a hypothetical match between the two bought teams.
Personally I think a format where players actually played against each other would be better, perhaps done in a way that allows anyone to start a team with a set amount of money (say $10,000) and they have to put together a team. Through this way, good players will have to be cheap at the beginning so that it can get going and prices will rise as matches are played and teams win more money (kind of like in FIFA Ultimate Team). I also think having sponsors would be a fun addition. Say, a player can choose to be a sponsor rather than a purchasable player - a sponsor could receive a set income per week (eg. $5000), this would make it necessary for teams to secure sponsors so that they could buy players. Sponsor deals could be made (an example: Team A secures sponsorship from sponsor X. Sponsor X provides a regular $3000 per week to team A in exchange for 40% of all match winnings). This idea means that small teams will benefit more from a sponsorship, as they will receive more money than they are forced to pay out. A sponsor may wish to tactically choose how he makes his deals so that while he may end up losing money at the start, by supporting a team (which may later become very strong), the sponsor will then be able to make considerable money if he invests correctly. A player may choose to be a sponsor as the money they make could then be put into creating their own team.
Just a few ideas I think would make this really interesting and exciting. Of course it will depend on what whoever actually ends up making it prefers, but I think in this kind of way it will give everyone something to do and can allow players to make money without playing for a team and then perhaps use this to form their own team.