Hybrid components are added for extra power to te the ICE.
You ask for return of the V10, I think that you want the kind of V10s as in the last stages of their existance, thus 19000+ rpm 3 liters.
Such engines had more than enough power on their own and were not in need at all for hybrid components.
For hybrid assisted V10s you would need an entirely new, way less powerful concept of V10 with new specs. (And no doubt they had to be so that lots of noise and rpms to make that howling noise too, somehow I can't envision that all those fans who beg for the return of V10s would like to see versions that rev at only 10000-11000 rpm instead of that 19000+ when they screamed the most and the loudest and appealed the most to such V10 fans.)
Anyway, when you need another spec of V10, yet another manner of starting a spending war beause of the need to start all over again. Like what happened for the current PU's. And we all know by now that, based on the lessons learned by Mercedes, you need budgets beyond belief for that.
I have the feeling that continuing with the current V6 ICE it eventually will be cheaper for the ICE part of the PU's that drop the V6 and start all over again with yet another ICE concept to be integrated within a PU package.
The current engines aren't getting any cheaper. How many more teams need to drop off before the cost and complexity of this formula are actually acknowledged?
The 19K RPM engines were around very briefly towards the end of the V10 era. I don't recall anyone complaining about the noise of the 1998 Merc engines or the 1996 Ferraris, neither of which turned anywhere near 19,000rpm. The early 1990s cars sounded pretty good, a damn sight better than the current powerplants.
Just because it would expensive to change to *something else* doesn't mean we have to accept an engine formula with price tags in the tens of millions of dollars. It's all well and good to have a rule for a cost cap, but what's the point if no one is prepared to accept on a cost basis, the V6 Hybrid era has been a disaster.
There simply isn't that much money in the world to be spent on motor racing to sustain that cost. Grids used to be huge and I feel that everyone has gotten used to there being ten teams of less, when it should be seen as a massive indictment on how much unsustainable spending has been locked in by the top end of the grid. The engine and gearbox costs are a huge part of that, and any rule changes that don't acknowledge that are basically a waste of time.