It can be done but your alarm will no long be thatchem approved and it depends if you can get hold of the old remote starter module as most only stock the new G4 range plus you would have to remember not to leave it in gear as well. Don't say you wouldn't leave it in gear because one day you will as I did started car up only for it to jump in gear to hit the car in front of mine. The new G4 remote engine start works with manual and auto gear boxes which I have fitted to my car now.
Any alarm system with a remote engine start will not be a cat1.Your best bet would be to speak to Danny at AMS (mention my name) on 023 92669600 he will tell you your best option . There is away round it I'll pm you tho on how to go about this.