I would go with Kuduae's option first and if that is not achievable then re-barrel to same cartridge with new exact contour etc barrel. The second option of course destroys the 'collector' value as such but this may not concern you so much.

I have the same Mauser Type A opened up to 404J and it does boot and bruise off the bench even at original 404J specs let alone if you chase 2300fps or more. In your case if wanting to retain the original barrel and options 1 & 2 are not want you want to do, you could possibly re-chamber and bore your barrel for the 10.75x68 cartridge. This was an original chambering for the Type A (mine was this before opening up to 404J). Conversion to the 10.75x68 would be much simpler (if the chamber would re-cut?)as this cartridge, like the 9.2x63, uses the unaltered standard length action. Cases are not so available as the 404J but they are out there.

With modern powders and bullets it appears from other posters using the '68 that you can achieve the old 404J specs of 2100fps with 400gr bullets, or just stick to the modern Woodleighs in 350 gr weight for lighter recoil.

Best wishes which ever way you go, you have a fine rifle I might say.