Mmmm nuclear weapons in flashpoint... That was the first thing I made when I de-pbo'ed my first unit.
Its rather simple to make a nuke in flashpoint.. Create a new missile object using the SCUD model. Make the indirect damage something like 100000, and make the indirect damage range a big number. Put explodes=1
VIOLA!
Far from realistic tho... I mean since when do people launch nukes on troops?