Timothy - Weeds and Dormant Question

2015 hay is in the barn. Pretty much broad leaf weed free - but still some "grassy" weeds that 2,4-d or Pasturegard won't touch.

The plan is to spray the fields dead with roundup and no-till in new grass hay. Tillage is not possible as we are the Saudi Arabia of rocks. My concern is - I'll spend a ton of $$$'s reseeding, lime and fertilizing and end up with a ton of good hay, but also a ton of "grassy" weeds too as there must be a bazillion seeds on and in the ground.

However, if I plant timothy, I get a high yielding, essentially one cut hay and then it goes dormant as the summer heat comes on. I'm thinking that I use this dormancy to my advantage. As the summer grass weeds come on and shoot up through the dormant timothy and grow taller, I come along with a weed wiper and selectively take them out. For all other broadleaf weeds, they would get sprayed. Perhaps over several seasons, we can "use up" the remaining grassy weed seeds and have a nice field of timothy - and if later, choose to plant something else that is summer active, the weeds are no longer a problem.

What do you think?

Thanks!
Bill

Timothy - Weeds and Dormant Question