I started Excavation sites not long ago and I like them just as much as the Tree/Headbutt, & dig sites.
My suggestion is to have more of both in all regions. Tree/headbutt, & dig spots in Hoenn, & Excavation sites in Kento, & Johto. They would give more hunting opportunities to all players. As for the Excavation sites, I think the same thing should happen as in Hoenn, by gainning a "Archaeologist Permit" of that region to use the sites, and to be fair the excavation discoveries count should stay in that region, so new region new discovery start.