I like that set of rules. It's simple and digestible. Also include facebook marketplace and local pickup ebay sellers as buying options. Anything that enables local buying is fine.
Travel distance should be set to a maximum (1 way), I'm not sure on the regional geography, which would help with keeping that distance competitive, so someone would have to come up with a reasonable number. I like separating travel costs from PC budget.
Ultimately, it's not about the rules or how novel they are, or if "we already did it last year". What makes the Scrapyard Wars event great is the interactions and reactions that happen during the event, so anything that can facilitate that would be great - perhaps a twice daily video message (snapchat, hangouts, etc.) from each team to create a bit of competitive back n forth.
Maybe adding in a series of competitive mini games similar to how the junkyard wars did on their TV show - that gives the winning team a selection from some "power ups" like seeing the other team's build list, getting an extra $100 dollars, or swapping a single chosen component from each teams builds (blindly). (perhaps a winner gets to spin the prize wheel.) These could be split out over several episodes.
Ideas for mini games
Manually water cooling a PC (by mouth, blowing fresh water through some tubes), whoever ends with the lowest average temp during a CPU stress test wins
Best hand painted/glued/taped/etc design on a sponsored case (the case could be included by a sponsor for both teams, so the focus is only components), thinking like a white blank NZXT case. Ideally these designs would be parody or funny, perhaps making fun of the other team or presenting your team's name in a funny or GAMER way. Some theme would help facilitate creativity.
voting could be done in house or as a viewer poll
A mini game of "family feud" with PC/mobile/tech related questions with answers aggregated from viewers
"The Fastest PC" race - a mini multi-lap parking lot race, with pc cases fitted with coaster wheels, that contestants ride like a small trike while wearing full body pads
The mini games would add some moments where the teams could nag each other and give opportunities for interactions.
I would definitely like to see another season, and hope that Linus would reconsider doing it again. It's one of the events that cemented my interest in LTT on youtube.