If Csound is recompiled while the host is playing, it can lead to problems. Although, there shouldn't be any issues if the host is currently stopped. The real issue is if you add control parameters to the instrument that is currently instantiated. VST cannot handle the dynamic updating of parameters. So if your plugin uses 4 sliders, it will need to continue to use 4 sliders for as long as it's instantiated.
If you are not using parameters and simply want an instance to Csound inside your DAW that you can recompile on the fly, maybe you could look at CsoundVST by Mike Goggins?
As outlined above, if Csound decides to recompile while the DAW is 'playing' you will most likely get a crash.
Agreed. The quickest way is usually to simply reload the session.