Absolutely no way you gonna be able to convince 1 billion people to run full nodes without any incentive ( and if you offer an incentive it would have to be a damn good one too). And I don't think focusing only on people with decent internet is a good idea, Bitcoin needs reach everyone. The obvious solution for people with really bad connection is to simply use online wallets. Blockchain's inner workings and software wallets will only ever appeal to the techie types anyways. Right now people are wary of hacks but as we move toward a government regulated Bitcoin, we'll see better protection/insurance.
yes bitcoin should reach everyone.. but trying to push 7 billion people is harder than 1 billion.
this topic is more about making people ful nodes rather than a different topic about making people want to spend bitcoin.
so sticking with the topic about full node adoption.. trying to get 1 billion is easier than 7 billion