If you’re looking to make an IBL, you’re inbreeding the line, which means selecting parents that have the traits you want to lock down and breed true through filial generations.
Preservation is trying to maintain everything you can save from the genetic code, so you’d want all of the fathers pollinating all of the mothers.
That being said, if it were me I’d keep the seeds collected from any mutants separate from the rest of the OP due to the likelihood of runty/mutated/weak plants in those, but still keep them around to see what’s in them in the name of diversity.