Building an FM transceiver
Most of the answers are treating the transmit side. Basically however, the fundamental problem is that building such wideband tranceivers, fm, am or whatever is just very difficult.
I suspect that you are not going to find any transceivers that cover a continuous range up to 500 MHz. If you did, they would probably include FM along with everything else cuz once you have the basic circuitry in place for a transceiver, it is easy to add different modes.
On the legislative side, there is a sharp difference between broadcast FM and FM for voice communications. Basically, FM designed for voice is narrow band, it does not occupy a much greater bandwidth then a similar AM signal. It is a little bit better from a noise perspective than AM., but it is quite spectrally efficient.
Broadcast FM, on the other hand, occupies a much greater bandwidth because it uses a much higher deviation ratio. This provides much better noise suppression when you have a good strong signal. However a broadcast FM signal is somewhere around 100 or 120 kilohertz wide (I cannot remember exactly).