Neither the ram system or the EPAS system are perfect, they are both a compromise. With both systems the force needed to move the steering wheels stays exactly the same. As you point out the EPAS is the wrong side of the steering box but it can only provide about an additional 25Nm of torque, I suspect a suitable strong individual can provide over 100 Nm of torque into the steering wheel. If your are a serial stationary steering wheel twiddler then this may not be the system for you. The EPAS will always fail safe, it has layers of protection built in and while they have been known to fail the mean time between failures when put into the context of Land Rover reliability is exceptional. Mines an early generation of EPAS, the more modern ones are very much smaller and easier to accommodate and I suspect even more reliable.
Don't know much about the Heystee hydraulic system and their potential failure modes but you would hope it would fail safe but these units are from a bygone era, I think this one was initially designed for the Santana and I guess it uses a spool valve so it could fail and restrict the movement of the ram and hence the steering. The steering is now linked to the spool valve rather than directly to the swivel so that probably introduces some disconnect into the system and of course you are trying to steer a link with three flexible pivots which cant be ideal. The ram can produce 15KN of force so if you keep the steering demand on when its on the swivel stop that's like having a 1.5T press pushing sideways on your dumb iron and swivel stop and steering arms.
When it comes to originality and holes in the bulkhead I'm not worried, my Land Rover is a daily user, its not an investment purchase and while all the metal in my bulkhead can trace its heritage back to the dawn of time itself most of it has been added in the past decade and I suspect that's true of nearly all Series Land Rover that have or are being used, if you have a Series Land Rover that's original you probably have a museum to keep it in.
I was a little surprised to see the price of both the EPAS linked to and the ram system, both are more than I would ever be willing to pay.