What you are discussing here is whether flamers by themselves are overpowered to the point they negate any other strategy on a map that follows your guidelines with all other things, power levels and research, being equal. My contention is that they are not a be all and end all weopon with the current settings, although with a window of opportunity they can be devastating. But I leave out of my comments incendiary mortars, something I have not yet experimented much with.
An experienced player on a full base start knows there is a possibility of a flamer cyborg rush, for another example, and these are easier to stop the further from base they are caught. There are counters to all flamer tactics and to me that suggests balance. What gives the impression of imbalance is that if someone is caught off guard the flamers destroy units so fast that people forget they are a short range weopon that is useless on everything but non tracked units and pits and bunkers.
Another example, I have been rushed by 10 flamer cyborgs very early and all I did was set trucks to infinity build and build my own flamer bots. In a few minutes my bots killed his bots and the game went on as normal. I have had this happen to me while using flamers a lot too. Ie, the prouduction rates themselves can outweigh the offensive capacity of an early flamer rush. This is true for low oil too, same principle, lower numbers. It can be done with mg cyborgs, if care is taken to micromanage them out of the way of flamers. A rush is always a liability to the rusher if it fails, as its always done at the cost of base building and mid game research and production.
I did flamer vrs mg experiments 1v1 high oil vrs overlord, and that ended with the score being 2-2. If anything after him adapting to flamers the game is biased towards mg. No rush tactics, just standing armies. If flamers close range they win. If they don't they lose. To me this binary situation shows balance. Not to mention that unit body research and weopon types keep pushing the flamers back in effectiveness. Try using massed flamers vrs assault guns and bullet upgrades for example, it becomes next to impossible. Any high rate of fire weopon tilts the balance, as a flamer unit will tend to be light and fast, as the situations where tracked flamers are usuable are few and far between (bunker assaults under artillary fire for example, mixed in with other tracked units as cyborg flamer defense come to mind). Plasmites have another window of opportunity, but by then if the player is not doing thermal upgrades or betting on concrete it is his fault. A mantiss hover will keep distance to a plasmite, and with heavy cannons can mow them down in open ground. A tracked unit and some defense will break even. As research piles on plasmite will become obsolete. As stated before it won't work vrs rail guns. Even needle gun cyborgs can do massive damage in relatively low numbers to plasmite hovers. I have been on both sides of this situation and know what I'm talking about.
I will leave just one comment on the incendiary mortar thing, contradicting myself, sorry, which is that I have seen them be destroyed a lot by tracked units, be it heavy cannons, assault guns or even normal mortars. They are devastating to cyborg heavy armies and hovers, but I have seen them being taken down and have done it myself using these methods. By the time they appear on scene ripples are a reality and will work because they, the incendiary mortar, need to be immobile to fire, which ups the hitpoints they take. And there is always vtols... Hvc vtols can take down a surprising amount of stationary units.
A lot of players play rigid strategic approaches, that when fail they will not change. The better the player gets, the more adaptable the builds get, and the harder it is to exploit unit and weapons strength and vulnerability. Flamers have vulnerability in spades if people keep calm and carry on up the jungle.
And lets not forget the elephant in the living room of all balance discussions which is the unit transfer button... Most people play team games and now we come to situations where teamplay is fundamental. Most people that transfer try and do it in a way that is disguised to the other team, so as to hide vulnerability. Much of the perceived imbalance is the numbers game that unit transfer alters so radically and other teams not noticing that 100 units at 8 minutes had to be a transfer so its safe to leave base and help teammate. Many of the balance issues would go away if there were objective multiplayer tutorial availables to the noob and intermediate player, so that they realize what is possible. I used to have a pdf somewhere with the tech tree made with actual in game graphics, which is something that would help immensly too. An accurate 3.2 tech tree schematic, either in game or as a pdf file with the installer would focus players a lot, eliminating a lot of the unbalance complaints, especially if people realize that in some games its possible to open research research research factory factory...
I'm probably repeating myself already so I will consider my opinion given now