Have done 'connections' on separate tickets via various PRC airports over the past years.

Now that I think about it, really haven't had any major problems with this approach.

I've never been to CTU, but would be quite happy to give either option (Lucky Air or Sichuan) a try. Would prefer 3h vs. 2.5h. I would expect 2.5h to be fine also.

Some thoughts:
- my experience of the efficiency of Chinese 'regional' airports has been fairly positive (i.e. no massive waiting times)
- if there is a terminal change, budget extra time for this (thinking of e.g. Xiamen, the bus ride incl. waiting time can take up to 30min)
- if your corporate TA can't book e.g. Lucky Air, ctrip has worked well for me
- book domestic business / first if available and price difference acceptable to you (check in will be quick and you will have priority security; lounges are not that great obviously; certainly on Sichuan the seat is pretty decent)
- I try to avoid flying domestic Y, but even those experiences have been perfectly fine (Kunming Airlines and Xiamen Airlines most recently)