That is interesting. Which parts of the process would you want to be involved in, and why would it make such a difference in the time needed for the delivery of the feature?
Right now we have a designer making mock up pages for me and we have a deadline. He is adding a fair bit of stuff that will need to be done with a mix of back end code and JavaScript. If we do things slightly differently I can code most of it in Django. If we do it exactly as he has done, i will need slightly less Django code, but the same amount of code again in JavaScript. Plus I find it better to have as much logic in the back end, rather than jumping between JavaScript and Python to work out where bugs are.
The designers must always collaborate with the engineers, if that's not happening it's bad project management :(
I also approve your tech/engineering choices :D