When looking up information on bands like Therion, it might be useful to know when exactly the band switched from death metal to symphonic metal. Right now I have to use wikipedia, as all MA says is that they played one genre "early" and another "later", so I propose that an extra data field for genre be added to the individual releases of a band.

It has been discussed before and is not going to happen. See here: viewtopic.php?f=3&t=99962