Biggest issue I would be worried about is capping/sealing the hole left by the tank pressure gauge, that is 800psi tank pressure in there, and any bodge/filler/cap is only a nudge away from becoming a 800psi powered projectile (+ the change of pants required due to the noise of 2Kg of liquid CO2 venting !!!).
Most regulators the gauges are screwed in and I suspect their removal will immediately invalidate and warranty.
Biggest issue I would be worried about is capping/sealing the hole left by the tank pressure gauge, that is 800psi tank pressure in there, and any bodge/filler/cap is only a nudge away from becoming a 800psi powered projectile (+ the change of pants required due to the noise of 2Kg of liquid CO2 venting !!!).