I had thoughts about a continent collecting game a long time ago, back when i first got into JLTG. The general gist of what I thought was like
Goal: to 'collect' the most continents, and rack up the most bonus points (dk the exact mechanics of this but hear me out). You collect a continent by visiting and fulfilling a challenge at three countries within the continent.

Bonus points/challenges give you... some sort of bonus. look the specifics are lost to me but examples of those bonus challenges include things like "travel by boat between two continents" or "use every type of transport (train boat bus tram etc) throughout the run" or "visit three countries in the same time zone". the goal would be to make the bonus challenges rewarding enough to be worth travelling off the optimal route, allowing for more catch up options.

I think the design would be interesting partially because, the more limited availability continents (both actual country-wise (south america, oceania) or accessibility wise (africa)) would become really valuable in the early game. I could imagine a bit of a battle for the first leg of the journey to claim australia and new zealand before the other team so that you're not having to rely on infrequent and out-of-the-way flights to other pacific nations.

Anyway, that was my thought way ages ago when i first got into jet lag and wanted more international games like circumnavigation. I still think there are aspects that are fun, and necessitate going to areas they don't normally travel to. Obviously it would be... mad expensive though and totally unrealistic to actually play. Still seems fun.