Can you be more specific about what you actually want? Because “more security” can be anything. As far as that article explains, Titan M indeed is using ARM TrustZone, with the ability to do Tensor operations. So that means it will utilize the TEE for local AI processing. Fairphone isn’t doing the heavy AI processing that Google Pixels do. So unless you want that AI magic, there would be no need to develop a Fairphone TEE. ARM TrustZone is already really good.
IMHO the only thing FP should improve are more regular updates and something like FIPS 140.