Quite frankly, I was a bit surprised to see the side-balancing mechanism being implemented so quickly.
Even moreso, was the strictness and harshness of it - in your very first posting about this matter you've just suggested a time limitation before being able to take off again. Somehow, in actual implementation the 'time limitation' has changed to 'plane removal according to ENY' - which is IMO a much more radical solution to it all.
Merely a few hours has passed, and the reaction of the players are very extreme. While careful voices urge people to calm down and see what it might add(or take away) from the gameplay, most people are infuriated it seems.
Some squadrons, specialzing in a certain plane, have announced that they would move from their country of origin if the numbers obstruct their operations. For instance, the 412th has announced that if the Sunday Rook numbers persist and it limits their operations, they'll move to Knits/Bish side.
Now, purely considering the effect of it, it looks like exactly what you have pictured it to be. A squad will move to the other country. Numbers will be balanced.
However, in a more intimate aspect, the 412th for instance, is forced to break all their former ties with Rooks...and as for the Rooks, losing the 412th is losing a very valuable asset - the shocking part of this is that the decisions were more or less forced from a direct means of intervention to balance the numbers, which I find it a very odd and rare thing to come from HTC.
I view the reactions of many people quite sympathetically. While I support the side-balancing mechanism, I can't help but wonder "does it have to be this harsh?". It's those kind of reactions which I was specifically worried about when a side-balancing mechanism was under discussion.
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I can't seem to shake it from my head that there's an alternative to this.
Basically, in your very first posting about side balancing, I've suggested an alternative means of limitation in numbers by perks.
Essentially, the expected effect is simular to what it is now. When their favorite planes become perked, and gets more expensive with increasing pilot numbers, many people will probably have to choose to fly other planes, or jump sides.
People don't care about ENY changes. It's a simple analogy coming from observations of basic human nature. People don't much care about how many perks they earn - as long as they have a fight, and got nothing to lose from it. However, if a plane becomes perked, he loses something if he gets shot down.
People are more sensitive about what they might lose, rather than what they might gain. Thus, however meager it is, if perks are applied to planes it will work as a limiting factor.
Now, unlike removing a plane from use, this 'limitation' is set on relative factors, and relies on what people might choose.
While removing a plane from use directly achieves its results, slapping a perk on it expects people to voluntarily use other planes, or switch sides to use what they want.. and thus, it is not a 100% sure-proof method of forcing a balance, but it is more lenient and less infuriating in that people have a choice - whether to risk perks, fly other planes, or jump sides. They still can fly the planes they want, if they are willing to pay a price for it.
It is doubtless that you've already considered this alternative, and decided that it wasn't strict enough to force numbers balance. However, perhaps you might have overlooked the side-effects it might bring, and also overestimated the need for an absolute balance in pure numbers. By the current method, it is very possible you might be able to achieve almost perfect numbers balance in the MA.. but along the process a lot of things may come in jeopardy.
What's done is done. And the side balancing needs to be tested out. But if it continues to be problematic, I recommend that you try using perk points as an alternative.
The basic mechanism remains same, but instead of removing the planes of that certain ENY when arena is imbalanced, a perk is applied to that previously free plane of certain ENY - if imbalance continues to grow, more and more planes become perked, and the newly perked planes become more expensive.