Think about the characteristics of the existing units for a moment.
What is the rant about? Big, can't jump much, lots of HP, powerful slash. The powerful attack and high HP balances with the relative lack of mobility and big target. You touch any of these alone and you get an unbalanced unit.
To adapt the rant to S2, if you make it "weaker", which means lower the HP and damage, you also need to push up the mobility (I'm guessing you don't want to touch the size ie. bounding box). So you get a rant with lower HP, weaker damage, who can jump and move faster.
Sound familiar? To me it looks like the normal goon, only bigger and not quite as fast. I for one don't see the point of a 3rd, fatter, slower goon.
The size alone makes it unworkable. The rant is so big that the moment it enters a base everything and everybody will shoot (and hit) it, from turrets to the builder's blaster. So the high HP is a must have and even so the player needs to estimate very well when it's time to withdraw (if he wasn't on a suicide run). In fact, one might argue that the whole raison d'etre of the rant is as a heavy assault unit.