Photoshop can create the image to have the contact sheet etc. for use on any printer.
But it is then up to the printer to be able to be able to handle the paper.
You are right, the dye-sub can only do a certain maximum size, which isn't A4.
You could go the other way, a large high-quality printer, I have the Canon pro9500 Mk II, can be LEFT ON, for long periods of time, without being used. Every so often, it vibrates its ink tanks to keep them mixed, and in theory shouldn't waste much (any) ink in this. It can print at A3+ (13 inches by 19 inches), and has archival quality pigment inks.
With the correct setup (you have the colormunki) and paper, it produces very nice results. It would allow you to print images for your clients 'quickly' (well, it is quoted at 7 minutes something for A3+ full res), faster than DSCL anyway.