How highly would this mod/project be frowned upon?

[archamond5]

Hey guys I haven't posted much here but I've come accross a bit of a dilemma I have a 318ti '95 model. It didn't come into my care with a factor alarm installed. However it does show signs that it did in the past and that it was removed from the car entirely or that it was put in a location that i'm not familiar with. eg under the metal knee bolster on the drivers side (i saw that today). Now I was going to do this befor I bought an alarm and started splicing wires in the factory harness. I was going to make an alarm/keyless entry system using an arduino so that I could open the car with my phone. now last night I bought a factory brain and harness as well as the glass break sensor and a couple other things that go with it, no siren though. the problem that i'm having is it might be a 3 button alarm system and as such I have not been able to find a keyfob for it. Same with the two button brain. So here is the mod that I'm going to propose and see what the reaction is.

I an thinking now about taking apart the alarm brain and removing the green connector from the PCB to use for my own board. Then making a new PCB for the arduino controls and components that will fit into the factory box. scrapping the remaining PCB and installing it as one would if it were stock.

What are your thoughts on this. I'm also open to other options or ideas on where to get the keyfob for the system I just don't want to spend an arm and a leg on the fobs. Thanks for reading and sorry that it was a little long winded.

Edit: It is from a '97 E36 so it should be a two button system. However based on the FCC ID ending in 070 it means that it is a three button system so it looks like the custom internals are a go.

What are your thoughts on this mod?