I have a totalled 02 wagon and was wondering if its possible to swap the alarm system over to my 04 wrx wagon.

Is it just as simple as finding a control module, starter kill and speaker and plugging in wiring harnesses (or splicing wires), or would I be better off just buying an aftermarket alarm system?

And on a side note, does anyone else think its absolutely rediculous that they left out the feature from some wrxs? It already triggers the alarm if you hit the panic button, why would Subaru not make it a standard feature to sound the horn when opening doors?