To specify my trouble, I need to have the same PI but with different tech_requirement.
If I have any temple in my PIs, just altered the requirement and icon, then it shows up in my techtree, however cheating to get playing as terrans shows terran techtree with original temple. That is ok, but if I build 'my' temple() then the terrans are still able to build 'their' temple.
This is a bit confusing, since it is still the same PI, S_internalname is same

So my conclusion, the game reads the default PI.xml for the races and a mod PI.xml for my race and puts them together. But what happens to my 'shadowing' PI? I suspect that the shadowing PI can't have a different techreq but same s_internalname ?
I know, a possible solution is, to leave the name attributes of key techs as they are.
Another exampple:
I just put in the OrbitalFleetManager and changed the displayname. No problem so far.
But will the AI be able to build their OrbitalFleetManager, if I defined it again with different tech_requirement?
BTW, the OrbitalFleetManager seems to have a hardcoded ability, because if I change the internal name, it won't fleet if attacked. Does the planetary logisticsability work as intended?