What about this type of wiring/setup for base?

LattimerII

Since the base model only has front speakers, I was thinking of doing something like this:

Kenwood or Clarion headunit with about 22 watts RMS per channel.
Components in door and dash
Powered sub somewhere in back.

Here's the real question. What if I wired the tweeters to the front channel outputs and the mids to the rear channel output since I have no real rears to power anyway? Any disadvantage to this?

Sub of course would use the sub output.