For research topics, I would make two versions: A low-power, bulky device that has to be carried in a backpack or something. This one would require Psionics (and all of its required research topics), the brainchip research, and potentially an interrogation of a Sectoid Leader or better. This one could work with any armor, but is not that great.
For the ultimate mind-shield, it requires researching alien electronics, flying power armor, and interrogating a high-tier psychic enemy (Ethereals or the Embassy brain should suffice). That one is naturally way better shield, but more expensive to make, and may only work with power-armor type suits due its intense energy requirements (if you wish to code in that limitation). Alternatively, it could be integrated into the best power armor types (the Flying and the yellow one types), but that would require changing the stats of the existing armors, or creating a new one with minimal differences. I dunno which option is better.
