To make it less personal.... imagine that a government wanted to extend the advantages of GE to more of their citizens as possible. They don't have the money to subsidies it right now so they offer something like your plan. Still, assume that <10% of the population is going to be engineered.

Group by genetic intervention since you don't know which will be best.

For each couple a projection of their childs likely earning potential given their parents economic status vs the rest of the population is calculated.

If a significantly larger portion of the subjects of that same intervention beat the trend the company gets to claim X% of the tax revenue from those people for their working lives. (note, the subjects do not pay a higher tax rate than other people with the same income)

It's a long term investment but if the intervention is good it could be worth a very large amount.

The companies interest is in making sure those kids surpass expectations.

Does this bother people the same way the OP's suggestion does?

It strikes me that you might even be able to do this with non-GE cases. Companies could be offered a similar deal for intervening in the lives of poor, inner city youth through educational programs etc. If they win, everyone wins especially the kids and the value of the contracts could vary as the company applies new interventions or new evidence comes to light about old interventions that have been applied to subjects.