I am an ex-A2 QFI. I hold a valid professional aeroplane licence and a current display authorisation but no FI rating.
As far as civil regulation goes, the ex-A2 and DA are irrelevant when it comes to flight instruction.
How can you possibly think that you can offer your services as an 'aerobatic instructor' when you hold no civil instructional privileges whatsoever?
Under part-FCL, as a minimum, you would need to hold a CRI certificate and a (legacy) Aerobatic Rating and to have demonstrated your ability to a suitably qualified FIC instructor.