Hi Felix, the "hole filling" one is definitely something I am planning on working on for MoI, if you are referring to the Rhino N-sided Patch command. That's actually a command in base Rhino, nothing to do in particular with T-splines.

The T-splines toolset involves a fairly different style of modeling than NURBS modeling, it's focused on creating things from a sub-d polygon cage. It's an entire toolset and workflow that revolves around that different type of modeling approach and there are a lot of different pieces involved and that makes it not particularly feasible to just cherry pick one individual feature from there.

An N-Sided patch command though is one that will fit in MoI's toolset, the only reason why it's not there yet is that it's fairly difficult to make a good quality one but I do expect to dig into it at some point here.

- Michael