I like the idea presented by Zhou Chie about writing from the perspective of the 'common man', funnily enough. One of the things I found surprising was the CCTV-produced 1980s TV series of Three Kingdoms - given the novel's stance of pretty much ignoring the needs of the common person and focussing mainly on dynastic rights - this had many scenes depicting the plight of soldiers in battle having boiling oil poured on them, and peasants having their crops stolen by hungry soldiers. In some ways, those scenes really helped, whereas in-novel scenes such as an overly reverent peasant man feeding bits of his wife to Liu Bei and passing it off as wolf meat were, well, not so endearing. If you can get a copy of that series from somewhere for some inspiration, I recommend it: some of the lead actors chop and change a bit, and it's still a take on the novel, but the actors do the job so well that it works, even with poor effects and bad subtitling. I found it on eBay.
There are so many interesting figures that you could focus on, and maybe not even the obvious ones. The Yellow Turban Rebellion sounds like a good idea if you went down the 'common man' route, since that can be done from a number of very interesting viewpoints, such as looking at the motivations of the Turbans, maybe, and the general discontent with the Imperial regime that gave the Turbans a platform. On the other hand, Chibi is a good place because of its monumental significance: there are so many parts to it that you could write a whole series and still stand apart from the recent John Woo movie, which took some large liberties in the story-telling department to shave the time down. The problem is balancing factual story-telling with what people still want to see in there regardless: do you have the arrow-borrowing scheme, just because it's popular...?
Without this sounding like self-promotion - it isn't, I'm just sharing an experience - I've already self-published a 'less myth, more fact' novel about Zhuge Liang last year, and that was after being told by a half-dozen big agents in the UK that it was 'well written, but about a subject that we do not feel has a large enough customer base to warrant our interest'. ...???? ...Perhaps that was a polite way of telling me to 'do one', but they usually don't do polite, it has to be said, they usually ignore you. And if you are forced to self-publish, remember that promoting it is the hard part: I've already accidentally committed cardinal sin number one by signing up here to tell people about it without contributing first, and the bottom line with self-publishing is a lot of hard work making people aware of it without sounding like you just want their money - only big publishing houses can do that.
I sincerely wish you all the best: the era is fascinating and needs more people shouting about it. I'll be keen to hear how you get on with the agents & publishers: may you have better luck than I did!