A small correction of my previous comment: the discarding of F8 is not possible,
I missread the parenthesis. The other problems remain.

I think, we should first get clear about the condition the formula should
achieve. The things I see are:
- The costs should be proportional to the damage amount.
- The costs for bigger bots should be not smaller than the costs for smaller
bots (ideally a little bit higher).
- The costs for repairing one damage point should in no case (different bots
etc.) differ more than factor 2. (60% of the max cost of one point is ok, but
45% would be not).
- The time costs should not exceed 30s.
- The healing rate have to be considered (ideally it should be seen as healing
itself during repair in the same way it heals normally).
- [The circuit costs and heat costs should be proportional to the time costs.]

I have skipped "damage repair should take approx. 1 second[...] per point of
damage to repair".
Are you alright this these conditions? Do you see other conditions the formulas
would have to fulfill?