If someone is riding your planets shields and you transfer the shields to another planet, will they be attacked by offensive fighters on the planet once the shields are removed?

I don't believe it will do anything until they attempt to attack the shields. Someone would have to test it to be sure.

Actually. nothing happens to them at all, as long as they do not touch a key.. not even the / (ie can't do anything to redisplay the Prompt)...which is why corpies need to use TA to track where the rider's moved to.

Can't even keepalive, to my knowledge, except maybe char 27.

Otherwise they'll get blasted by offensive figs and any cannon blast. Offensive figs have limits to their attack odds tho, which is why atmos cannon is usually a better choice.

Anyway this presents you with some nice opportunities. Secure a 2 deep tunnel, put some planets (at least one with an IG) and a crapload of figs in the sector, then put the planet w/ the rider in the sector behind it. Make them work at it, torp the planet hourly so he can't just xport out, etc. With any luck you might get 2 kills, the rider and their rescue attempt.

or if you can afford it, blow the planet

Using attack planets with no or very few cols makes it a viable option.