Anyone have an idea to adding weight(s) to trailer tongue?

It can be done. I had a 200# platform carrying a 180# genset welded to the rear of my prior TT.
I did have to re load my cargo to balance everything but once this was done TT was very stable.
However whatever you use to create balance (weight in the front) needs to be permanent. Don't rely on a fluctuating ballast like a water tank.
I will add my platform was on a large 32' 11K GVW TT which gave me lots of room and weight to balance things out.