The 2600 will work with anything that is ISO compliant.

Current seeding equipment that I am aware of that is ISO compliant consists of:

2009 and newer CNH seeding equipment
2007? and newer White planters
2009 and newer Horsch Anderson seeders
Great Plains planters should be since they use Dickey John monitors
2009 and newer Deere seeding equipment w/ Seedstar II monitor systems

Deere equipment on the Seedstar platform will all work with the 2600, though anything older than 2009 will have to be done through "emulation" mode which is rather clunky and limits screen layouts. Planters which use the Seedstar Generation II can be upgraded to Seedstar 2 to run on the 2600 display just like the new planters do. I ordered the upgrade for our planter and it was $1333 or thereabouts. I'm not familiar with what monitor your 1690 would have but if it's not Seedstar I'm sure it would be cost prohibitive to upgrade it.

With the addition of a rate controller and swath control to the 2600 it will control sections on just about anything using hydraulic valves, tru-count clutches, etc. When you want, all you would have to do is move it to your sprayer and go. We saved enough using it in our sprayer this year we are adding another display.

As for your wish about the monitor in the tractor, your wish is only a few months away, but you need all the implement manufacturers to get on board. The ball is really starting to get rolling on that.