A change to the way MusicBee handles years isn't necessary in my opinion. The desired function can already be achieved with a custom-virtual tag combination. Letting MusicBee automatically group years together would take away some of the freedom it currently offers, which would be a shame. Besides that, who is to say the highest years among the individual tracks is also the desired year for the entire compilation.
To create the desired effect, a custom tag would need to be created, which should either contain the year of the individual track, or the year of the compilation album. You could for example use Original Year for this purpose, from the custom tags drop-down list. For sorting you could then create a virtual tag which reads the custom tag for compilations and the Year tag for other albums.