1. E-Memory Functionality
E-Memory ports are currently the purview of a separate module. I think that should simply be combined with the cyberbrain. E-notes are so ubiquitous and module is in such low-demand there is more merit in actually making one piece of chrome useful.
2. Robotic Command Acceleration
As discussed here (https://www.sindome.org/bgbb/game-discussion/game-problems/robot-command-entry-delay-603/) when combined with an ARIN interface - robotic commands should be considerably faster in relation to the tier of cyberbrain you possess.
3. Lite-Term Functionality Baked In
The Cyberbrain is already reliant on SIC signal - why not fully incorporate decking into each module? Quickterm -> LiteTerm -> l33tTerm tier seems to line up well against cyberbrain tiers in this regard.
4. Cyber technician Rig
The ability for one-person to jack into another (control yourselves, plz) is a staple in things such as Ghost In the Shell. I think it makes sense for the Mneumonic Cyberbrain to have this as a feature, and allow a skilled tech to actually adjust their own chrome internally on the fly. The latter would be available on lower-end cyberbrains - but they would lack the any influence outside of their own systems.
5. Relational boost to processor power
With the above feature, cyber tech and skilled techs with cyberbrains should be able to overclock their brains and dedicate increasingly more processor power to it with a relational boost to their intelligence. Naturally, there would be a threshold maximum here.