I think you ought to be able to get the same/similar/perhaps even better result in shadow detail by increasing GI settings (relative detail most likely). I understand why reducing blur radius helps, but it's clearly impractical to have it below a certain limit. So reduce it until just before you see tile boundaries, then increase relative detail (and try playing with sample quality too perhaps) until you get the detail you want. May not work, but worth trying since you haven't cracked the basic scene lighting setup yet.
All that being said I found the middle image to be most appealing, even though it was darkest and, I gather, not what you want. It seemed much more realistic than the other two, which both seemed artificially lit in the shadows, sort of HDR-esque.
As others have said, I think dealing with this in post is going to be the most expedient and effective option. The trick will be to get the quality high enough to give some info there in the shadows to work with, and to reduce noise as much as possible so when you pull the shadows up, it won't get too grainy.
GI Caching should take care of any flicker, with the right settings. It's not necessarily totally intuitive, but as Matt suggests, rendering cache files every x frames (e.g. 10 or 20) rather than every single frame and then blending lots of frames (e.g. 5) should work. It basically makes sure the GI is averaged over a larger time scale.
- Oshyan
