We have a customer with a trike... I hope the area you are in is level without many hills!
Normal issues with machine/trike: power, water, waste and space.
Customers machine is gas fired - gas isn't as effective, it's slower to heat up and recover and the gas bottles are heavy. Gas also scares the sort of people who control to gate at outside events so over here in the UK you need the correct documents in place.
Their gas powered machine still needs a power supply to work the machines filling mechanism/electronics (minimal electronics on a lever group machine?) - provided by heavy batteries and an inverter that last a few hours...
You'll probably need some form of inline water pump to provide enough pressure to fill the machine from your water tank. A pressurised boiler needs to have water forced into it.
Apart from all the usual hassles associated with a trike it can be rewarding and fun. You can also find yourself cycling down a hill a bit fast with a pressurised boiler waiting to brand the back of your head with the word "Gaggia" or similar, backwards!