I had the same questions when I first started kiting a few years ago, posted it here:viewtopic.php?f=3&t=6507
I thought it would be nice to have a jetski to get out around here on SW days for example. I've since concluded it is not practical, not a good idea on the big lake. Roberto has summed it up well presently and on the previous thread. You are just asking for trouble. Offshore wind is gusty, which is no fun, and to get clean wind you have to head offshore. When shit goes wrong in choppy conditions in cold water way offshore, you are asking for trouble. Managing a ski and a kite with its lines, etc., especially a beginner kiter, bad scenario.
I think by far the best way to learn/progress is to take a trip someplace with steady wind and preferable flat-water - i.e. Hatteras, Padre, Key West, many places in Caribbean. Jetskis are often used in these places to take you back upwind quickly after you've drifted downwind. Around here, seek nice long beaches when the wind is clean - side-on wind - so you can ride, drift downwind, walk back up, repeat. i.e. Waukegan on S or SE, Zion (though shorter stretch of beach) on N or NE, and many MI beaches on a SW. Indiana beaches can work too but as many people have stated the wind at the bottom of the lake can be less predictable.
Hopefully see ya on the water.