.NET programming

HI,
I read some paper on .net and clr regards managed code; I can notice 2 different types: type value (allocate on the stack) and reference type (objects). allocate on the managed heap. It seems to me .NET team work a lot on this thing (and it introduced managed c++; This I think to have the potentiality garbage collector join to potentialityof c++).
But my question is: If I want allocate Objects on the stackinstead on managed heap (i.e. change the CLR features), what changes Do I have to do on memory management or on other? Do anyone around the world thoght to this solution? Any suggests or link?
thanks

ok maybe the question was vague. Indeed, Do anyone know if there are other runtime (eg mono???) that work on allocation in a .NET different way ? And wich?

thanks.