OTA style metal patches obviously has it advantages, especially as it makes it much easier to control the flow of metal from the mapmakers perspective, I don't you should scrap the Spring style metal concept just because of that though.
On the wind issue I belive somewhere around 0-20 or 0-30 is pretty reasonable for a map where you want wind to be the "best" option, which it wasn't on all TA maps. Although wind was viable on most maps with the expection of the moon maps.
Relying on wind for your energy needs has always been a risky move though, even on maps where it has proven to be useful, because you might just get stuck with all of your generators giving an output of +1, thus ruining your economy for the moment. I hope it stays this way in TA, and personally I find the suggestion that you'd need 30-40 as an average output for wind to be viable quite odd, as online play in TA has shown that's not true.
Just for reference, two maps where almost only wind was used in TA are GoW and PD. In GoW I belive the wind varied between 1 to 27, while on PD it was between 1 (or 0, not sure) to 24.
I really should ask one of the old OTA players to know for sure how they looked on the viability of wind as I myself never was never better than average. From what I've discussed so far though, most seems to agree that once the average income goes to 7 or above, wind quickly becomes the better option. Some do favor having a few solars just as a backup, but overall wind quickly becomes the better option for your main source of energy income. It can lead to the added investment of energy storages though.
From this you can easily come to your own conclusions, there are however some minor points that I would want to add. First of, you have to take into account that solars in XTA doesn't cost any energy at all, this is however something that mostly comes into play if your current source of energy is getting destroyed, so you lack energy.
The other thing I want to add is a short overview of the advantages of the two different sources of energy, ordered by (from my point of view and without taking into account the lack of energy cost for the XTA solar) importance;
1) The wind generator costs less, only 1/3 of a solar. An average income of 7 will thus already put it as the better choice theoretically.
2) The wind generator builds quicker, this means you will start to get your energy income faster too which might matter quite a bit.
3) The solar gives you a constant supply of energy that does not vary.
4) The solar is better armored than the wind generator. I'm not sure if 3 wind generators have more health than a single solar though (you also have to take into account that they are often built next to each other, so when one goes it will damage the ones next to it).
5) A single solar takes less space than 3 wind generators. Once the average wind income from a single generator is 20 or above this points becomes moot though, but before that it can potentially be important on certain maps.
6) A solar usually leaves a "better" wreckage, thus yielding you more metal when you reclaim it. This of course means it was destroyed in the first place, which never is that good.
This is all disregarding the tidal of course, but that's another matter entirely as it needs water to be built. It works by the same principle as the solar however, the difference being that the wind generator is only › the cost of the tidal. There are also some other differences compared to the solar of course (size, armor etc), but generally it should be pretty straightforward to decide if its worth the cost or not if you already understand the relation between solars and wind generators.
One more note about wind, if I remember correctly. In OTA the wind was highest on the barren worlds (ice/desert etc), while it wasn't a real option on moon maps.
I changed my comments to reflect reality a bit better
