This is a weird question.
It has been established that a caster could cast Simulacrum on themselves to make a simulacra, then the simulacra can cast Simulacrum on the caster to make a second simulacra of the caster, and son on. Let’s call this a chain of simulacra.
Certain spells can be made permanent by casting them on the same place daily or weekly for a set period of time, such as a month or year. These spells include Mordenkainen’s Private sanctum, druid grove, forbiddance, guards and wards, temple of the gods and mighty fortress.
I am not certain of the wording on these, but could a chain of simulacra make any of these permanent?