On the right (ie. Mirror of the STE 15pin ports) would mean that they could keep the electrical layout ie. Connected to the keyboard, and hence a separate keyboard unit. For 2 player games you would be swapping it a lot- there were adapters just to help with this.

I agree it would be difficult to design a correct socket, but from interviews it was always the plan to have a blitter, and a socket as standard would have helped adoption.

The main thing is that the T212 is a great coprocessor, faster than the 68881 fpu and with a 2k cache. Introducing the transputer as a coprocessor would potentially have changed the computing landscape