these alternatives preserve the element of blacking, while avoiding any implied racial mimicry, stereotyping or disrespect.

Could I put in a mention for the superb Pig Dyke Molly? Firstly for the excellent and inventive quality of their dancing, then for the tight precision of their high quality musicians, the fine showmanship of any of their dance stands but also (and here is what is relevant to this thread) the thought and execution that goes into their costumes and face painting. This page from their website shows photos of their displays for 2016, all as they say, in "glorious black and white".

Surely this would met the Shrewsbury requirements (even if they have not already appeared there).

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A slightly more worrying aspect is that the Shrewsbury statement (linked to above) was brought about because -

the festival was accused of racial harassment and threatened with legal action by an organisation called FRESH

I would have thought that an accusation of "racial harassment" was putting it too high. The fear of 'legal action' seems to have been behind this Shropshire statement.
Did the organisation Fairness, Respect & Equality in Shropshire go to the police or the Institute of Race Relations with their concerns about what was happening at this folk festival or are we to regard this self-appointed body as the arbiters of what constitutes "racial harrasment"? Does anyone know the sequence of what happened?