I think, overall, if I wanted to play an arranger from an 88, I would simply get a decent arranger and MIDI it to something like a Yamaha P105 or your choice of inexpensive digital piano. Most arrangers have the ability to 'mirror' their main keyboard on an incoming single MIDI channel from something like this...

But it always strikes me that most of the 88 arrangers I have seen are usually at least a generation behind their 61/76 note counterparts. So maybe it's better to get an S950 or a BK-7m, and run it from a REAL digital piano..?