No single entity needs to take the burden of developing the whole regional infrastructure themselves, they just need to do their own thing, for their own market, and accept Bitcoins for their own wallet.

There are exchanges in almost every country in Southeast Asia already, albeit each are fighting local battles with local regulators. They barely even know each other, but each victory strengthens the ecosystem as a whole.

I believe Square's cash app is the best approximate for this phenomenon. There are Square clones in almost every country, the moment they follow its lead in accepting Bitcoins is when the interoperability of Bitcoin will be more appreciated.