In a perfect world, each team would have unlimited budget to attract unlimited talent and we'd have 13+ teams with utterly unique cars that lap with a tenth of second of each other.
Kudos to F1 for recognizing we don't live in that world, and creating opportunities for teams without the organizational know how to build an entire F1 car from scratch to acquire that knowledge from outside sources.
If teams are worried about 'B' teams being beholden to their suppliers, perhaps there is another solution than simply eliminating the concept all together. Put in a limit how much a team can rely on a single supplier.
The Haas (and RB) are as much Ferrari (RBR) as possible. Maybe make it so that only X% (50?) of purchased parts can come from a single supplier, so that the Haas would have to use a second supplier, besides Ferrari. It wouldn't affect operations/cost, but eliminates the perception of a conflict of interest.