Indeed, the Pokemon story is incredible in terms of an investment opportunity. One of those "right place, right time" and you're in luck, phenomenon.
You're spot on with slabbed coins. You can see this clearly illustrated with the 1937 Five pounds to half sovereign proof set. You could get a decent near FDC original set for somewhere around £17k. Split up and slabbed by NGC you're looking at twice that amount for the four. It's ridiculous.