You can ask for a translation of the theory paper and the AB will provide that.As far as i know the ABRSM theory books are published only in English and - I think - Chinese. (I am ready to be corrected if that info is not accurate). Anyway, I have never found a French version and in any case I gave up using even the English AB theory books ages ago as the Lina Ng and Ying Ying Ng books are light years better.
For practical exams they usually send us a French speaking examiner. If the examiner is fluent then all is fine and above all capable of understanding the replies to the aural tests that's fine. where the examiner is not very fluent or has difficulty in understanding the child our local rep goes in to help out - though she did one year come out of an exam to ask me for a translation of a child's answer as she didn't understand what he meant. I train all my candidates to cope with the language situation in the practical exams and it has never been a problem. They are, after all, used to my own gaffs!
I don't think they could remove the theory requirement for non English speakers. it would be unfair the other way round and open to abuse. I have a rather confused attitude to all this. I support the theory requirement in principle but I think it is unfair to my students. I don't see how it could be changed unless for every one and I don't really see why Trinity and LCM should higher grades should get the same number of UCAS points without a theory requirement.
It's a bit messy!