Whilst I would not use the word silly I do think that you would regret it in that you would be acquiring a specialisation without the well rounded knowledge that comes with ACCA (or ACA).
Personally I fully intend to do ATT as CPD. I would not consider it an alternative to ACCA but rather an add on.
How far are you through ACCA at the moment? Are you at the skills level or professional level?
At the higher level you will see how papers start to interact and how taking Tax in isolation from (say) advanced corporate reporting could be a mistake.
That is just my opinion,
Hope that it helps a little,
kind regards,
Shaun.
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Shaun
Responses are not meant as a substitute for professional advice. Answers are intended as outline only the advice of a qualified professional with access to all relevant information should be sought before acting on any response given.