Immobilizer relocation

[Fiddlebog]

This is an idea that I've thought about ever since I heard about the common problem of wet immobilizer units. I've (of course) seen the waterproof cases to help prevent immobilizer damage.
But why not just put the immobilizer somewhere other than in the bottom of the body: the most likely place for water to pool? Why not just put it next to the ECU, or tuck it up in the dash somewhere?
Now that I'm actually working on a Boxster that needs the immobilizer replaced, that's what I'm thinking about doing. Is there a reason I haven't seen anybody else do this?
Maybe I'm just bad at searching.