mm.. reading thru the suggestions and comments you give, I do not understand why you want a synthesizer?
If I understand well what you are saying, you are looking for;
Styles which are dedicated to your own compositions?

Why not just use your arranger board and make your own styles?

or;

You could save yourselve a lot of money by going the software route!

Have a look at band in a box software or jammer pro software.
Or you could just use your va76 to record each track in sequencer software.