Originally Posted by
markk
That's a small number of wires for an ECU, in the industry over 250 was not uncommon that I was working with.
The joins are not uncommon either, I just hope the feed and GND are both big enough if there are only one of each. Though, the load calcs work out easily if you connect the right amount of highsides and lowsides correctly for outputs.
The sensor 5v is not really an issue distributing it, though as you are fully aware, takes a lot of planning when loom building!
Good luck
I did design but not build looms on the Tornado Project many 1000's of wires in that but a very large budget
. Funnily enough only the dbw motor would cause a problem in this application & thats feeds through a relay so no such probs. My loom
experience is a long one remember crawling around in Concorde 2 back in the 60's rather more wires in that 
.
Only started on cars when I retired I designed & built Marks looms to a price for 6 years before he made me redundant through old age last November .