I think the problem with very runny poo is that nothing can absorb the fluid fast enough to prevent any leaking. So your fleece and paper wont actually help absorbing any of the liquid and act more as a dish which spills over.
I do know though that when we were on holiday and Anna was very poorly I wished I had some 2 parters to use instead of disposables as they didnt keep the mess in either: she was covered from waist to ankles within milliseconds
The only thing I can think of is stick with your nappies + wraps as they will be better for immediate absorption of fluid than disposables and just rinse them out as soon as you can then wash them a bit hotter than normal to get rid of the bacteria.
Hope she gets better soon