What you're trying to eliminate is just a small part of the infra arms race. But it's not even effective at that. You say one of the goals is to not have to squeeze many racks into a building, but your proposal assumes the servers placed in the racks are running at low capacity, which is completely not true. On the other hand, if you trade say GOOG, the matching engine for that is going to mainly sit in one place, how do you stuff everyone's program to run on the same server, and how do you make sure they each have fair access?