Tannic acid would likely stain the gelatin emulsion. Whether or not it will effectively develop film to a desirable result, and under which conditions, would take a lot of experimentation to figure out. Due to its tendency to stain pretty much everything it comes into contact with, it would not be very suitable for development of slides/reversal processing. The tanning effect might also hold back development of the denser areas, which can result in poor blacks. For reversal processing, I'd stick to a normal, non-staining developer for both first and second development. If desired, the film can always be toned afterwards with any toner that would work on silver, such as sepia, selenium, gold etc.
Furthermore, as far as I know, tannic acid is a poorly characterized substance that can be highly variable in composition. This would exacerbate the problems above as a formula that works one day (after lots of testing) may not work quite as well at a later stage when you happen to have a different batch of tannic acid as a raw material.
I don't know how strict customs are in Turkey; it would be nice if your Pyrocat makes it through.