Looks like
encoder - 1 (MPG on the side of the panel)
analog inputs - 3 (JRO, SRO, FRO)
digital inputs - 36 (plus a few more on the MPG for selector/increment)
A 7i73 can handle the control panel, but it can only drive 3v LED's. If you want 24v LED's for the illuminated pushbuttons you'll need to use a 3v->24v opto or something similar.
A 7i84 could also handle the control as shown, as it has enough digital & analog inputs plus encoders to handle everything. Plus it can source 24vdc for the LED's.
In both cases you'll want to plan on using a matrix keypad configuration - neither board can do the entire panel without using the matrix solution. The 7i73 is very easy to set up, but I believe the 7i84 can also be set up without too much trouble using some of the inputs and outputs along with matrix_kb.comp.
Remember - just because panel buttons are wired in a matrix... doesn't mean they have to be physically laid out in a matrix.
If I were building that panel, I'd use a 7i84 and keep everything 24v - even though sourcing those little square buttons with 24v LED's can be a bit of a bugger. And the wiring is easier as the 7i84 has screw terminals.
Regarding board(s) for the rest of the conversion, you'll need to make a list of all the IO (voltages, digital vs. analog, sinking or sourcing), plus how the drives are to be controlled.
