"...I can joke and say I want T-splines for MoI? T-splines for rhino are so buggy (v2.0) when you work in symettry and delete a face it hang'n'crash. And when you start to have a complex model (like a coca cola bottle) it gets very slow even on a quad with 8gb of ram... "

If you find Tsplines to be buggy, it probably has very little to do with Rhino. So I don't think having a MoI plugin will necessarily fix that. But the Tsplines V2 code seems MUCH improved and more stable than V1. If you have this repeatable crash using symmetry, just turn symmetry off and delete the other half as you work. You can always add symmetry later... Also I feel the best workflow is to rough out your model in a poly/subd modeler and then import as Tspline to add local refinements...