Thanks for the reply. I've done more research, looked at Arduino examples (I have lots of Arduino, but PIC seems better because of the great IDE and PBP!)
The PIC will be talking directly to the port expanders (which use MCP23017s) that communicate with I2C. I realize now I don't need a 40 pin MCU, any fast MCU with I2C comm and memory to hold my program will do. I've seen some 8 pin PICs that MIGHT do the job!!

At issue at this point is the matrix switching I have to do which I'm doing it now for another Christmas Display. My new display will be a 5-point star shape with 6 segments, counting the pentagon in the middle. Each segment will have a port expander and 16 channel triac board. The incandescent lights I'm lighting will be RGB, so in order to light any individual light bulb I must enable the segment(s) and light color(s) (one board) and hold those triacs on until I can enable the individual light "triads".Doc1.pdf See attached PDF file where I show the "boards" on the segment they are to control. Each of the lights shown (yellow or red) is actually a "triad" of RGB lights.

So basically I enable the segment and light COLOR, then enable up to 16 channels with another triac board which then turn on the lights. Can I do this with I2C? Or I should say with the MCP23017? I have to hold a value (data and address) while I set the other one up, then enable them both at the "same" time. I don't have any of my hardware setup or purchased yet so I can't test it.