Reply to "Theoretical question. Hydralic roller vs solid roller"

Sure, titanium valves and retainers would be the way to go.
Light valves aren't going to make the hydraulic lifter 100% efficient though. There will still be a loss.

If you go to roller lifters you are adding far more weight to the valvetrain then you would be eliminating in the titanium valves. Those assemblies are heavy and not known to be reliable for high reving engines for long durabilaty cycles. They break a lot. They are certainly not low maintanence items.

With roller lifters the valve springs need to replaced more often and the higher spring rate beats up on the valve train more.

There is more potential for catastrofic valve train failure with roller lifters.

You need rocker arm stud girdles and even then you can snap rocker arm studs. I can testify first hand on all of these points.

Last but not least titanium components also tend to be a little pricey.

On the plus side I suppose it sounds cool to say you have a roller lifter cam?