no, gilf content is vomit inducing.
GILF is not the same as elderly. RL humans can be grandmothers before they're 40 without underage pregnancies. Luthien is an actual GILF once Liandra has her kid. So is Erevi, technically, after ED's egg come along, and Shakala once SD starts contributing to goblin tribe size.
I suspect adding a girl in her 40s or even early 50s (or equivalent for non-humans, like Luthien) who already has grandkids would be welcomed by the players if she is still attractive/sexy and can have kids without needing fertility boosts. A GILF who needs a supernatural assist to have kids would be a harder sell.
If someone's GILF fantasy revolves around also banging her daughter, that's kinda common. If it's about also banging her GRANDdaughter, with or without the daughter, now that's perverted even before considering whether the GILF can still have kids without intervention.
The amount of time needed to develop that would better be spent on something the majority of fans actually want.
For revising an existing dusty pussy into a girl you can knock up? Absolutely!