Thanks Sam. What if I insist that the construction of $T^* C$ should not depend on any monoidal structure $\otimes$? For example it doesn't seem like such a structure is available in part 2.

In characteristic zero the category of Mackey functors is semisimple. The simple Mackey functors over any field have been classified by Thevenaz and Webb -- they are one-to-one with conjugacy classes of pairs (subgroup $H$, irrep $L$ of $N_G(H)/H$). I think a sphere $\,\, S^V$ acts on the simple Mackey functor corresponding to $(H,L)$ by a shift, but a shift that depends on $H$: the dimension of the fixed-point space $V^H$.

I have nothing against Schubert cells, but the attaching maps are very complicated. I would be just as interested in hearing about a regular cell complex structure as a triangulation, but it's easy to get from one to the other so I asked about triangulations. If you know a triangulation that refines the Schubert stratification, so much the better!

I was a little off: a nontrivial irrep matches to O(-1) on a reduced P^1. The trivial irrep matches to the structure sheaf of the scheme-theoretic exceptional fiber, shifted by 1. More stuff like this available here arxiv.org/abs/math/9812016

There's an equivalence of derived categories (G-equivariant coherent sheaves on C^2) = (coherent sheaves on a minimal resolution of the Duval singularity). It sends a nontrivial irrep of G (supported at the origin in C^2) to the structure sheaf of a component of the exceptional fiber. I wonder which sheaf on C^2 corresponds to a skyscraper on a node in the exceptional fiber. Whatever it is it has maps to and from the irrep.