Running a Gen-1 on lead acid

In our local EV club we've been throwing around some ideas and I wanted to through them around over here and see what comes up. The idea is to use a cheap prius with a dead traction battery as a cheap DIY electric-vehicle. First a little background:

When I bought my 2002 in December, which had a bad traction battery, I charged up the battery cell by cell with an R/C car charger. Unfortunately, the pack was still too low voltage to start the engine, nevertheless the computer attempted to start it several times. It just never got quite up to the required RPM to turn on the fuel injectors.

The interesting thing about this test is after the first starting attempt, I read the codes on the computer and found that it said there was a battery ECU communication failure. I looked in the back and sure enough I had forgotten to plug in the battery ECU. However, the car attempted to start even with this condition.

Then of course, after having the car running with the new battery recently I did the test of disabling the fuel pump and doing a test driving the car around on EV. Even though the engine fails to start, the car remains in READY mode.

So, that lead us to wonder about the possibility of finding a prius sort of like I did that is really cheap because of a dead traction battery. Then, instead of replacing the battery with a stock battery, just fitting in some cheap lead-acid batteries to get up to the same 273 nominal voltage. Just get rid of the old toyota battery pack and battery-ECU.

The theory is, that you could disable the fuel-pump and drive the car as an EV on the lead-acid pack alone. When the pack is depleted, just recharge and go on. I'm not sure if the vehicle would allow regen since no battery-ECU.

Still, any thoughts on this?