You have also something that can be used and explored : Construct /Inset function ;)
Works on Selection Surface (s) (some training & tests are necessary ;)

Here not with your form


Variations with your form ( Shell / Inset )
Maybe in this order : Volume - Trim by curves - Separate - Shell (flip) - Inset

Here only Shell + Fillets (light inside MOi)


Shell + Inset