There are plenty of things they could do IMO and still keep it interesting.
1) LTT vs Gamers Nexus
2) build the best pc using only prebuilts as the base (think dell optiplex, hp z420, etc)
3) Have the scrapyard wars like normal but then try and sell the pc, whoever can get back the most wins. But when they go to meet the person, they just give them the system or something different from a sponsor.
4) Have them include a console in the build
5) size minded builds
6) legit scrapyard, only get stuff marked as broken or as is to see what they can repair or get items from broken things
7) one person gets all the stuff, the other person has to build it and vice versa. points based on what they had in mind vs what they did, looks, and the performance points goes to the person who bought the stuff
Just some random ideas