I have been thinking about how to obscure FOOM. As other have mentioned, I believe hiding the sudden rise in power would be almost impossible to conceal. That being said, I believe we can conceal the path to this rise in power.
There are a couple of secrets that we should obscure:
Sudden rise in power is related to shadow clones
Who knows: Gōketsu, Ami
How to obscure: minimize the visibility of shadow clones. We have already leaked some number of clones (4?). Restrict clones above this number to the Gōketsu compound or to the seventh path.
Sudden rise in power is related to chakra drain
Who knows Gōketsu, Ami
How to obscure: the chakra drain ability is quite visible in the leaf. We should neither increase nor decrease the emphasis on it. From the outside, it currently looks like it's main use is for topping off summoners. As long as we don't draw attention to it by trying to hide this ability, we should be ok. The main point in our favor here is that the Wakahisa clan has this ability and they are not all S ranked.
Gōketsu have and use an almost unlimited chakra:
Who knows: Gōketsu, Asuma (knows about the koi, doesn't know the magnitude), Wakahisa clan, others in the mist?, Ami?
How to obscure: slowly switch from buying chakra to selling a small fraction of the koi pond chakra as the fish mature. The goal is to make it look like our chakra pool is moderate, our chakra consumption has not increased, and that we are selling (giving?) the excess to the leaf.
Solution:
The trick is to offer a plausible explanation as to how so many of the Gōketsu clan suddenly gained power. Normally, one would call it a bloodline ability (Naruto's approach), but the clan is not related by blood.
What is unique to the clan? They have a disproportionate number of summoners and sealmasters.
Sealmasters - because not everyone in Gōketsu is a sealmaster, we would have to make it look like the rise in power related to a seal rather than sealing ability. However, this would paint a huge target on the two sealmasters.
Summoners - Another explanation could be that the rise in power is due to training from a variety of summons. Some of the ground work for this has already been laid (the Pangolin techniques during the chunin exam). If secret techniques from one Summon helped win the chunin exam, it is plausible that secret techniques and training methods from several are responsible for this rise to power.
Training with shadow clones on the seventh path both hides the shadow clones aspect and ties power jumps to summon training.
