Part of the appeal of Avon as avatar (besides the fact that he's most popular character, of course :-)) and also Vila could be partly because they are - along with Servalan - the most dramatically theatrical characters in the series.
This isn't meant as a criticism (goodness knows, I love the pair of 'em) but there's no doubt it's easier as a writer to pick up the *outward* aspects of both of them - both their physical appearance (Avon's especially being fairly striking) and their manners and mannerisms are more striking, and can therefore be copied *and recognised* more easily. I mean, you can write a Gan avatar, but who's going to recognise it? But a dark-haired, pale-faced, sarky bastard with a clipped mannered voice, a hint of tragedy ... (okay, okay, and maybe the mouth and/or nose).
Of course, there's much more to Avon that that, but these are the sort of things that are easy to cut and paste across :-) And other characters - Gan, Dayna, Soolin, Tarrant, even Blake - don't have as many of them (Jenna does, but the ones she has, the brassy blonde with a heart of tarnished gold, is such a traditional character anyway that any avatar would be lost in the general cliche).
As always, all IMO ...
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