Renewing old hay fields filled with weeds. Convert to horse pasture in future

Researching best practices for preparing existing hay fields that can eventually be turned into horse pasture.  Not sure what all types of grass or legumes.  Mostly Brome grass, I'm told.  There are also abundant weeds, poison ivy, rag, thistle, etc ...  Need to eradicate.  What I want to do is turn this into Orchard grass (not sure what variety to use) with perhaps a legume.  Thought about Clover, but don't too much of that.  I don't want Timothy.  What other Varities would work well with Orchard?  The goal is to use for hay, but be able to easily convert into pasture.

 

Any suggestions for a game plan is appreciated

Renewing old hay fields filled with weeds. Convert to horse pasture in future