Essentially OP is asking for gil limits on server transfers to be removed. Raising the price of the allagan pieces above their sell value just incurs a transfer tax, but still removes the limit.

Generally when people transfer, they can get around the limit by buying commodity items and reselling at the destination. It's inefficient, but allows a lot of wealth to transfer based on the relative economies. That inefficiency limits the use of the feature for the sole purpose of trading between server economies.

In the case of a Balmung -> Lower pop transfer, those 'friends' should be making a ton of money on the transfer. They can buy up high demand goods that are cheap on Balmung and sell them at the destination for much more. So there is absolutely no need for a gil limit boost or allagan pieces. Goods are relatively cheap on Balmung compared to any low/mid pop server. Why aren't they doing that?

Could it be they also want to transfer back to Balmung later after making the many millions of gil required to buy a Balmung house? That is why the transfer limit exits! It prevents Balmung from constantly dumping goods into other servers by capping the gil on return and even acts as a disincentive to transfer to high pop servers, helping control Balmung's population a little.