As far as I know, you WILL need the Hu-card port of a broken PCE, then you WILL have to remove the Hu-card port of the TG16, figure out the internal wiring and hope that it goes unnoticed. There is no way to only "reconfigure" the internal wiring, you need the physical entry as well. I had read somewhere also that the mod is permanent.
To tell the truth, you better go for a PCE Core System, they're selling for around $50 with controllers and games, much less than a Hu-card converter... and you also avoid wasting your TG16 system 🙂