What I'm trying to do is to combine two approaches, two frameworks into one solid scope, process ...

I have a bunch of tests in python with self-written TestRunner over proboscis library which gave me a good way to write my own Test Result implementation (in which I'm using jinja). This framework is now a solid thing. These tests are for tesing UI (using Selenium) on ASP.NET site.
On another hand I have to write tests for business logic. Apparently it would be right to use NUnit or TestDriven.NET for C#.

Could you please give me a tip, hint, advice of how I should integrate these two approaches in one final solution? May be the answer would be just to set up a CI server, donno...
Please note, the reason I'm using Python for ASP.Net portal is in its flexibility and opportunity to build any custom Test Runner, Test Loader, Test Discovery and so on...
P.S. Using IronPython is not an option for me.
P.P.S. For the sake of clarity: proboscis is the python library which allows to set test order and dependency of a choosen test. And these two options are the requirements!
Thank you in advance!
I don't know if you can fit them in one runner or process. I'm also not that familiar with Python. It seems to me that the Python written tests are more on a high level though. Acceptance tests or integration tests or whatever you want to call them. And the NUnit ones are unit test level. Therefore I would suggest that you first run the unit tests and if they pass the Python ones. You should be able to integrate that in a build script. And as you already suggested, if you can run that on a CI server, that would be my preferred approach in your situation.
Integrating tests written in Python and tests in C# in one solid solution