The GT5 had a plan for modular armor, but it was ultimately not completed. However, GT6 currently does not have such a feature. As for high-tech weapons, it doesn’t seem to be a tradition of GT, and currently GT6 already has guns. You may want to try GTweaponWorks, but I’m not sure if it’s still compatible with the current version.
Perhaps it’s time for some GT traditions to return, such as sonictron and data orb, but I don’t know how to integrate them with current gaming mechanics.