One way to "mix" arranger and seqencer is to
1. Make a new style of the sequenced part. (Itīs quite simple to do) You can take the whole part and save it as (for example) "original, basic, major".
2. Make this new style as a part of the style you want to mix it with. You simply have to "offer" one of your variations (for example "original, basic, major") and exchange it to your newly created one.
3. Now you have a new style wich is identical to your old style with one exception; everytime you choose "original, basic, major" you get the sequenced part in the key you choose.

The whole operation can take less than half an hour if you know what to do. (For an expert itīs a matter of minutes!)

Unfortunally I donīt have a VA-series keyboard so I canīt give you any help according to the tap-tempo. On my G-1000 you have to push the tap-tempo twice to get the tempo change. But the are two other buttons "rit" (ritardando)and "acc" (accelerando). A single push on one of these either fastens up or slows down the tempo. You can edit in detail how big the tempo change will be (ex. from 100 bpm to 130 bpm) and how fast it will occur (ex. during 1 measure). I donīt know if the VA have those buttons, but I know it is possible to make this settings on the VA-76. Maybe you can use your D-beam for this?

Regards, Michael