'Kingm' I think yr Q has been well answered here by those in the know.
If you have a logical think about it, guidance to the gate after Ldg automatically from an ILS would be extremely impracticable & damned dangerous. The amount of mobile equip en-route to yr gate especially around the apron area would make the journey in fog very hazardous.
Technology would be there that's for sure but there would be too many variables like closed taxi-ways/routes at random times, blocked taxiways due other A/C & the specter of equipment failure both onboard the A/C & any ground based tracking/guidance system just for starters not to mention human error. Simply the possible problems far outweigh any benefits.
Wmk2