> So let me ask this: How hard is it to create a temporary exit node that is basically a rasberry pi with a sim card or wifi connection say from a cafe, or any other public wifi, ans are online for say na hour or two?

It's not hard at all.

> If we had enough of these scattered around, would it matter?

No. Your relays won't be trusted with significant amounts of traffic until they've been up for a few weeks.