The junker is yet in advantage compared to a pyra or goldfish thanks to the combination of higher turning rate, high acceleleration, longer "ground resistance" and the possibility to rapidly bring 3 rebuild tools on the balloon with ease while maintaining hull and all engines. Pair it with the inherent weaknesses of the blender and a proper junker is to be approached with caution, i would call their (junker) chances 40/60
Goldfish are good against Junkers due to their speed and high disable. A competent fish is almost as good a hard counter as a cheese mobula (merc double art). It's hard enough fighting a fish with 3 engineers and two buff hammers including a spanner mallet buff. Fighting with a gunner and without buffs won't work against a good fish.
The fish doesn't need caution, they avoid fire and rush. 1v1 it doesn't matter if the fish gets disabled by the long range side. They rush in and have the heavy gun ready. Once the carro or burst hwatcha shoots the junker is locked down. The left side cannot kill a fish fast enough and the right side cannot disable. A good fish won't sit by and get shot.
Sure a junker can tank and maneuver but that's all they can do once they're locked down. They can only hope the fish makes a big mistake or ally helps. Turn rate and acceleration don't matter against a fish. Tanking is losing.
"the possibility to rapidly bring 3 rebuild tools on the balloon with ease while maintaining hull and all engines".
The hull engi can never leave position no matter what (they also help bottom) so unless the gunner moves up you can't have more than 2 tools.
Junkers should not fight fish 1v1.