As a defensive turret, Newton doesn't perform that well in comparison to others such as Faraday and it seldom gets any use outside of Newton ramps. Considering that it even loses to lotus when it comes to attack range, it doesn't really handle frontline role well.
In addition, when compared to Jugglenaut, the Newton has less survivality per Newton Gun in comparison.
Newton versus Jugglenaut comparison:
Newton guns: 2 vs 1
Can move: Can (move speed 34) vs Can't
Health per metal: 7,94 vs 10
Health per Newton gun: 15,88 vs 10
Considering that Jugglenaut can move and has jump attack ability on top, I think Newton should at least have health performance closer to Jugglenaut which is essentially double Newton turret with legs.
I believe that small range increase (from 440 to 460 to match lotus) and HP increase (from 2000 to 2500, 12,5 health per metal) would help the situation a lot. An armored form similar to Faraday instead of health buff would also help, but I can't imagine it fitting Newton unit model, unless the sides close and the ball turret lowers inside and somehow fits inside.
When compared to its frequently used utility turret Faraday, as it currently stands, Newton is better replaced with a Faraday that has 80 AoE attack, more range (460, even more if AoE affecting past that is taken into account), 8,8 health per metal without armored form and 35,2 health in armored form lasting frontline beating much longer and disabling enemy assault stacks with its 1200 Paralyze damage that leaves only 0,6 second recovery between shots and stunlocks with another Nearby Faraday till the end of game.
Compared to 3 Newtons (600 metal), 2 Faraday (500 metal) seems to be always better whether it is about beating frontline assaults, stunning enemy bomber strikes, surviving enemy artillery fire or just plain terraforming it underground to cover from enemy fire. Thinking about it, people would probably still keep building Faradays rather than Newtons even after a buff like that.
of course the other way to buff Newton would be reducing its metal cost, but that would probably end up making Newton ramps too easy to rush (price drop to 160 metal would also achieve the 12,5 health per metal ratio).