I'm just not sure, unless you are VERY good with MIDI, that a module and a remote is the way to go. Most modern arrangers are studded with switches, knobs and sliders, to control a bewildering array of options to do whatever you need to do. Volume control of the Parts, effects, insert effects (better get good with sys-ex to do anything live to those!), buttons to do everything from muting certain tracks (programmable which ones on a per-Performance basis) to split activators (with a per-performance split point) Melody Intelligence activators.

Truth is, there is still much in a modern arranger that either has no MIDI control at all, or it involves sys-ex, but the hooks to the sliders and knobs in the keyboard version is part of the OS. Try to duplicate much of it on a remote keyboard, and you quickly find out how much is missing. Plus, to get what full measure of control the arranger allows, basically, you have to have a fairly decent controller. A good 61 should be about $400+, to get a full selection of knobs, sliders and buttons and an action at least as good as the hardware version.

So, a grand for the module, $400+ for the controller... and a boatload of work to do to achieve far less than the keyboard version can do. Another $500 or so, you are into the full version of the arranger, with no programming work to do, no hooking up MIDI cables, and far better integration of control. The BK-5 offers far more control from the front panel than any controller can do, for little more than the BK-7m does by itself...

Now, I have a BK-7m. But I honestly wouldn't want to use if for a full arranger gig. It's the soundsource for my keytar, not a full gig solution. Those that want to go the remote keyboard route, best of luck and God bless, but I honestly think that the full version of the arranger is generally a MUCH easier solution, and at little, if any extra cost.