Lewis,
It's purely the fact Dave @ Ash said his kit wouldn't cope. The warranty thing was a side question. But the fact he wouldn't honor it is another sign it wouldn't cope.
Another point is, LC80/Y61 axles, converted would probably be under less than 35% of a full Ashcroft set-up cost. Assuming LC80 axles are about the same price as what Y61's can be had for.
The most expensive aftermarket route are retrofitting the Dana 60's. I cant find anywhere to get these myself, so I have to go with someone else's supplier. Supplied and kitted out for LR fit is circa £3,000. Which is around 10-15% ore expensive than a full Ash set-up, but will more than cope with it. These would be 30/35-Spline (bias towards the 35) with at least rear locker, front if one can be found.
Obviously if I got lets say LC80's with a full 30/30/30 spine 300M front and back, it would probably still sit somewhere around the Ashcroft route.
Difficult to know what to do.
On the legality side, I'd be cutting it close to a Q plate if I go with different axles too. That's put a bit of a sting in the tail too.