Replacing the bifuel CNG system with aftermarket LPG?

[dikidera]

So my 2005 S60 bi-fuel CNG volvo has it's CNG tank expired(21 years old). I talked with many techs and they want to install their own LPG(lpg because cng price skyrocketed + small tank) ecu and own button. I don't agree with this because :

1) It's ugly. They most often drill the dashboard to install an ugly button.
2) Horrible wiring skills and every car I've seen with LPG system was a mess of cables.
3) The car already has a button for this + CNG level meter on the dash. They told me they can't get that to work, so I will never be able to use the dash to tell how much LPG I have left. + the car automatically switches to CNG as soon as it warms up.

Do you guys think we can replace the CNG tank with all the components necessary for LPG, but fool our ECU into thinking it's still using CNG and let it control the LPG injection process and avoid aftermarket buttons and LPG controllers.

One of the potential many issues I foresee is the different quantity of liquid gas injected vs factory CNG as well as differences in how many sensors there are + their different readings(e.g a CNG system is much more high pressure vs LPG)