Your tractor(s) can definitely handle that much - my only cautions would be to build it strong and make sure your front weights are in place. 200 gallons of any liquid is gonna run around 1600 pounds WITHOUT the vessel, frame, etc. I'd also pay attention to ground condition, since you'd have about a ton of extra weight on the tractor.
On the other end of the scale, years ago I built a spray rig for a JD lawnmower - used a 25 gal. spot sprayer, built a pin-on "flatbed" just big enough to support the tank and boom hardware - drilled an extra hole in the top of the tank for return, added a gate valve from boom back to tank, and I adjust the return with a gate valve til it maintains 30 psi (only water in tank at this point) - then shut off the inline ball valve for tank return, add chemicals, close boom valve and open tank return ball valve - this lets chemicals mix with nothing to boom.
By the time I drive over somewhat bumpy ground to the "scene of the crime" the chemicals are mixed. I leave the tank return open thru the (adjuster) gate valve, open the boom valve, and drive.
Most of the above is probably redundant, if you ask specific questions we can probably help more... Steve