Unfortunately as far as I am aware vArranger is for PC only so would not be suitable for the OP.

Your best bet is Ableton for live play or Cubase or Logic for a studio base all of which can host VST Plug-Ins.

You will also need an arranger with good Midi Control facilities which in order of sophistication are: Bohm, Wersi (OAS 5 and above), Korg, Roland & Yamaha. (Not sure about Ketron)

In addition depending on what you want to do, a good Midi controller keyboard can be used instead.

Hope this helps

Bill