Well, I'd not set it in stone and try for testing both versions - the basic game allowing to play a simple battle is supposed to be free, right? So the same models can be placed on open battletop or hexes - a matter of scaling them properly.
So I'd vote for not throwing hexes away, especially that later on their sets can be sold along with the other models.
The hexes I imagine will interlock with each other making sturdy tabletop - not easy to disrupt with a sleeve
I'll make a picture of what I mean.