Great post! I've been pondering how to switch my D2 to a diffusion enlarger and this seems like a good way to go! To jp's point, the lag is probably the power inrush from the AC to DC power supply for the LEDs. I think you could fix that by using a relay controlled from the timer. So the timer is turning the relay off/on which would open/close the DC side of the circuit where the LEDs connect to. That keeps the LED power supply itself ready to go.

I haven't found a relay that is for switching a lower voltage using a high voltage for the switching though I'd imagine they exist (that or perhaps a transistor).

My concern here is those Ilford MG filters. I've gotten quite used to those so matching the wavelength there would be ideal. I wonder if warm-white LEDs might be closer in spectrum? I think the multicolored LED solution might be the best option. I think that's what the Intrepid 4x5 enlarger uses (actually wondering if I can augment their head on my D2...). And/or I wonder if RGB LEDs would work (you can find pretty dense RGB LED strips if space is tight, though not sure about light output). I'd still prefer filters over fiddling with colors. I think I would need/want a much more intelligent timer where I could easily dial in the desired filters for me to be happy with not using the gel filters.

In the interim, I read up a bit on making a diffusion panel for the Omega D2. I'm guessing something as simple as rice paper would either not provide even lighting or would transmit too much texture? If not, placing that on top of the negative carrier would work in a pinch?

I love the condenser look when it works but man can it be contrasty. Spotting hasn't been a huge issue (so far) but I definitely get more dust than I did on my Beseler 67. My tiny darkroom doesn't have room for two enlargers (and I prefer to print 4x5 most of the time anyway).