Good point. I'd forgotten about the Korg D1, also worth looking at. A bit heavier, but an action that may be preferable. (And I didn't mention Roland FP10/FP30, but Roland was already mentioned.) And like the Kawai ES110, the Korg also has the 5-pin DIN which he may prefer even if it's not required for this purpose.
Also possibly worth looking at (with 5-pin DIN MIDI) would be the Casio PX-360/PX-560, which have the older Casio action that some people prefer over their newer one... the same action as the PX-5S, but the 360/560 have the expression pedal input which may be a plus, though again, would not necessarily be a requirement as he doesn't actually want more pedals in the rig, and if he changes his mind about that later, there are other solutions as I mentioned. (The Kawai ES110, Korg D1, Roland FP10/30, Yamaha P45/121/125, and Casios below the PX-S3000 also lack expression pedal inputs.)