I looked into this EHPS(electro hydraulic power steering)as well but wiring the unit properly so that the pumps turns on and off, to wheel movement will be a pain. The pump can not run continuously without burning up either and it pulls close to 80 amps when operating at fulll load. It will be difficult also to wire in the steering computer that modulates the motor output control. It would be a sweet setup but the cost and labor overcomes the coolness very quickly.
From everything I've read most of that isn't actually correct.
At least for the MKII and MKIII pumps, there is a VSS that you can tap into to control the pump depending on your speed, and only have it turned on at low speeds. Additionally some folks have wired it so that they can control how much juice it's getting, meaning you could manually override it.
You could quite easily wire it so that you could flip it on, for on road or at speed you'd never need it, just flip a switch right before you hit the rock garden or start winching and enjoy the boost in pressure and flow. Leave it off the rest of the time.
As far as the amps goes, it can't pull 80 amps all the time or even at full load. The amp rating is the highest when it first engages at idle, the amount of juice it'd pull would be further reduced because the gear driven pump will already be spinning it, meaning that it will have little to no load when it starts (which is different than if it's the only pump). Additionally, the MR2 alts are only 70-100 amps, so if it drew up to 80 ams often enough it'd overwhelm the charging system, which doesn't happen.
The amperage would be low the majority of the time, even when rock crawling. You might have short spikes of high amps, but it'd be a snap to properly set it up to handle it.
I've read of several accounts of folks setting it up to draw 60 amps max, there were no issues setting it up that way. Considering that the gear driven pump will reduce the load, the max amperage should be even lower than that.
Oh, and the pump can run continuously without issue. Tons of people have these pumps running full time in their rig without issue. These pumps are popular with folks running electric cars or engines where mounting a gear or belt driven pump isn't feasible. If the pump is running and there is little to no load, it takes almost no amps and the DC motor isn't even breaking a sweat. It's a bit of a power waste to have it on all the time, but the small parasitic load it adds won't even be noticeable, especially since we'd be using it in low range at low speeds for short distances.
Sorry for playing devils advocate here, but seems that adding the extra pump for $40 (MKI) to $200 (MKIII) would do what you're trying to do and then some.
and the numbers we have dropped. We cannot reach the 5gpm like we had hoped prior to tearing into the pump. We achieved the 4gpm yesterday but today were not comfortable with the cam and housing after getting this flow. It can be obtained with a price but that is something that I will not pass on to a potential buyer and or mudder. 
