My idea is good, but it has a problem: the accelerator is outside the sheilding, so you have to cool it with it's own fan. In fact, if you want the wind-tunnel effect but don't want the sheilding you could do like this:
You put a fan where the RF modulator was,

but as I see it you have to close the grill in the upper part of the Amiga so the air only could go out for example with holes on the trapdoor.
Something similar to this:

You could do the same with the sheilding on with the fan on the rf place, and only you would have to cover the upper part of the sheilding leaving a place somewhere to let the air going out. With this way I believe I should have the coolest Indivision of all.