If you hold a JAR commercial with SEL and MEL, the FAA will issue you a private with SEL and MEL under 61.75. If you hold the B757 type on it I think they'll add the type rating. We used to issue commercials under 61.75 but have not done that since 1997. But there there are still some 61.75 commercial certificates floating around. If you complete the instrument pilot knowledge test or the foreign pilot instrument knowledge test you'll be granted instrument privileges. The Inspector issuing the certificate will remind you that you still a flight review with an instructor before flying on your FAA certificate.
There's no problem adding a type to to a commercial certificate. You are held to ATP standards during a type ride so the type will rise to the ATP level when you complete an ATP checkride, even if the check is done in a PA-34. The problem is issuing an initial commercial and type in the same checkride. The FAA commercial certificate is mainly a VFR checkride. You must do short field and soft field TO & landings, power off 180 landings, Lazy 8s and Chandelles and ground reference manuvers. Those aren't in the profiles for most jets and I don't think many sims are set up for them.
The no-landing clause was put in for military pilots who would launch on a mission, fly for hours and return to base. But civilian pilots can use it. Just log it in the X-C column. If the Inspector notices you departed ABC and returned to ABC after 3 hours just be ready to say we flew to XYZ and turned around.
Be careful about two private pilots logging PIC. About the only time two private pilots can log time together is while one is under the hood. The regulation says two pilots must be required by the aircraft certification (can't think of any SEL that applies to) or the regulation being operated under. US regs require a safety pilot while a pilot is under the hood. But there is guidance from the FAA that the safety pilot can only log that time while the other pilot is under the hood. So if it takes 15 minutes to taxi out, TO and put the hood on, the safety pilot can't count that time. Same thing at the destination, if he pulls the hood off to land and taxi in, that time can't be counted. There's also guidance from our friends that says the safety pilot can't count the time as X-C time even if they land 80 miles away. I have no idea why.