Change whale water system to gravity fed

Chris - before we had our van I was HUGELY. concerned about the Whale - so much so that I quizzed Whale about it at the NEC. They partially satisfied my concerns. When I was offered the hole in the wall I said YES - but it had to be as an additional and not a replacement so I said no. And I'm pleased I have got the Whale. It does take longer to fill but it will only accept pressurised fluids!!!
After 8 seasons I have to replace the hose itself which has developed pinhole leaks.

Can i be so bold to ask a techie question about a visa versa {now i no longer have a AS but Wildax
I currently have the "hole in the wall" and when it is full the tank overflows somewhere at the top of the tank so not pressurised. So does anybody think that it would be possible to add the Whale system like i had on the Dorset, sad i know but i did like it.
David