Errr that depends entirely on the scale and tempo of operations, I was thinking along the lines of 4-6 allowing two to be operationally deployed at any one time, we're talking about an escort for the solitary battalion battle group we can send overseas so in those terms two aircraft would be adequate for some tasks, while 4 would allow two to be in the air at once; therefore if you wanted to have a really worthwhile operational capability you would want six, so say roughly 100m all inclusive.
Not a bad price for safeguarding a full infantry battalion on an ongoing basis.
These would be an organic aviation asset, the government once felt that APCs and Artillery were something that should be provided by someone else but slowly all the pieces of a proper battlegroup have come in to place and it was only the shortage of something as mundane as trucks that prevented an artillery regiment being made ready for deployment to fill a possible gap in the SFOR/EUFOR ORBAT.