While I agree with Mike's suggestions, I'd add that it is possible to use sheet stock in a way that it only provides a surface, not a structural element. For example, one might construct a lattice-like structure that provides the structural strength, and simply cover it with thin sheet stock. That way, the thin sheet stock doesn't need to actually carry any weight.
When I made my latest table top, I wanted a phenolic surface, and planned on both a heavy router ad a heavy lift. So, I laminated two sheets of 3/4" phenolic-faced Baltic Birch ply to get the strength I wanted.