My zuk is currently getting a new fuel tank as I have killed three fuel pumps in as many weeks , yes it has a filter before it and thats not the topic of discussion here anyway .
Talking today with the guys and the idea of a lg tank as a fuel tank was floated , i said hmm something like that could be good , you could pressurize it and always have a head of pressure to the pump .
On the drive back from the fun trials up in Northland today I thought why not increase the pressure and ditch the fuel pump altogether .
On my nissan the fuel pump supplies fuel at a higher pressure than needed and the outlet of the fuel rail has a pressure regulator for the return fuel . This keeps the required fuel in the rail . If you regulated the pressure going into the rail you would not need a return line .
Then if you fulled the lpg ( or some sort of ) tank with fuel , hooked it up to a pressure sorce regulated to the fuel pressure required you would have fuel
There are a few issues with this
The fuel would be a constant feed , ie when you turn off the engine the fuel pump normally shuts off , not so here .
Having fuel and compressed air in a tank is probably not a good idea .
To get around these you could hook the fuel pump output from the ecu to a shutoff valve and you could use nitrogen as the gas to pressurize the tank from a small high pressure bottle , but I expect most people do not have access to nitrogen , argon or co2 would also work I guess .
This sounds like a lot of hassle to get rid of a fuel pump but after changing so many you look at everything .
Just posted this as a bit of humor and disscussion so post up your comments , its all good for a laugh .
I know air and fuel can be explosive but if you exclued the fuel vapour its a bit safer.
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New higher pressure injectors, circulating LPG lines at high pressure to ensure it does not vapourise, but not so much pressure that it freezes. 
