I don't buy that the available payload mass will be sensible when including the amount of power generation needed, especially considering that most satellites would probably still need a heavy chemical stage to boost them to their operating orbit.
Eh, solar panels are useful in orbit as well. They're particularly useful for avoiding the need for a heavy chemical stage because you can use them to power light weight ion thrusters instead.
If using solar, they can only accelerate half the time, thus amplifying the effect of drag, since now they have to speed up enough on the day side to also cancel out the drag losses on the night side.
On top of that I'm not really convinced they can put enough solar generation on there to drive the thrusters sufficiently, putting aside the additional costs of things like radiating off all the heat generated by the thrusters.
An orbital mirror could be a relatively simple option to allow acceleration during the night and multiply the solar energy during the day. Plenty large target, less atmospheric distortion/losses so shouldn't be all that hard to hit.
Hopefully you don't own a house in the path under the ship. It would be really annoying to have bright flashes of day light sweep through randomly at night. Also probably not great for global warming and insect life.
I don't think ion thrusters would work, for the balloon to maintain orbit you'd still be somewhere with enough atmospheric drag to be a problem. Ion thrusters only produce millinewtons worth of thrust, so they're very much relying on a no drag environment and the ability to run for continuous use for weeks to years.
ion thrusters won't get you to orbit or into an orbital insertion. They are only really helpful to slowly increase or decrease the speed in the direction you are already heading via some other propulsion method.
