Mutable Extrapolation/Interpolation?

[m-wells]

I am interested in having mutable interpolation types. I have a parent interpolation that I slice into and create sub-interpolations. See my package InterpolatedRejectionSampling.jl for context. Having a way to update part of an interpolation type in place might help with performance. Is there a way to do this without having to create a ton of mutable versions of all the required types from the ground up? Perhaps a couple of wrappers around the Interpolation/Extrapolation types?