IMO a 'fix' to this would just be to have a set number of 'PQ points' for the relevant race (or the same amount for every race), and that way if this is done the PQ of the planets in the system is adjusted accordingly.
Unfortunately, the terraforming techs would unbalance this. Having multiple low-pq planets would give higher eventual build-space compared to one pq 10 and one pq 4.
Whether this would be an advantage would depend on how rapidly one gets through the terraforming tech line to unlock the usable space.
More likely, a cheat flag will be added if you change the homeworld of a default race.
