/diy/ - Do It Yourself

There, I tried answering some questions, now I'd appreciate a bit of help myself.
Tell me everything that's wrong with this, why I'm stupid, why it won't work, all that shit, I wanna hear it.

For funz I'm trying to build something that can autonomously travel from Australia to the United States, I've spent a fair while experimenting with boats, and have had them zipping around lakes for months on end untouched, but the sea is just too abrasive for them to handle, so I'm back to aerial options.
Just today I started thinking about gliders, attached to a balloon to take it 20 miles/30km up, dropping it, and seeing how far it could get surfing currents.
If feasible, the idea would be a glider with propulsion (only used when necessary), a battery array, and solar cells on the wings. Carry it up via ballon, or just have it circle up in the Aussie desert on thermals and solar power, till it was well above cloud level for continuous sunlight, stay around a height that gave it plenty of leeway if the thermals were shit, but not so high the air was too thin, charge its batteries, and if its batteries were charged and it was still day, use all power from the solar panels to propel itself faster.
During the night, just drift down slowly, catching thermals if possible, but conserving power, not going below the tops of clouds.

I wasn't sure if RC planes could catch thermals, let alone something autonomous, but it looks like someone's already done so, with a shocking amount of success:
https://www.youtube.com/watch?v=V6tu7dL_MZE

My question is how many thermals are there over oceans, how high could I safely fly, what's a height zone I wouldn't hit commercial aircraft (Or just say fuck it and avoid commercial flightpaths altogether), and what else is wrong with my plans?
Are there better options for this? Do tell me your crazy ideas, fucking Gyrocopters, whatever, I wanna hear it.