Something along the line with this is what I would suggest. Please note that this example was built to handle a main line greeting for a branch office, including CUC to play the greetings and then send it of to some destination such as a phone, so it's not a perfect match for your ask, but with a minimal of adoption you should be able to make it work as you'd want it.
You absolutely need to adopt this to fit your needs, but in general something like this should work as you outlined your requirements. The big difference would be that you'd want ToD to only be used for calls coming in via the PSTN, so you'd need to put that construct that starts the whole ToD process into a partition that is only visible in the CSS used as the inbound CSS on you gateway or trunk whichever you have.
