I was concerned about fireforming before building my ackley also. Mostly because I had never had to deal with it before, I've learned now that it is not a big deal.
I do like the idea others suggested about doing a 6.5-280AI and using nosler brass. there are times when it would be nice to just go buy some brass and not have to deal with it. Not sure if that makes it harder to find dies or not though, and it also depends on what reamers your gunsmith has available, he may have to buy a 6.5-280AI die which could factor into the cost of your build, may be worth it if you dont want to mess with fireforming.
I went with a set of dies from 4D die company they were pretty reasonable on price (~$100) I don't know if they offer a 6.5-280 AI die specifically, But I do believe they make custom dies also. They are not as nice as some of the higher end dies, I would compare them to the quality of standard RCBS dies. But for the price they have worked fine for me, and it beat spending several hundred to have RCBS or another company custom make a set.
I have grown to not mind fireforming. I get extremely good brass life out of my AI so I do not have to fireform very often. When I do fireform a batch of brass, I load up 50-100 rounds in new nosler or norma brass with the cheapest bullets I can find, and a standard 6.5-06 book charge of IMR4350 (many other powders would work this is just what I have on hand). I make a trip to the range and use these rounds to work on form and trigger control etc. Surprisingly my fireform loads group very well, and I can practice consistently out to 500 yards with them.
Once fireformed I usually save half the cases for hunting and use the other half as practice cases. About once a year I make a new set of brass, my old hunting brass become my practice cases.
After initial fireforming I trim the cases to length. I check after every firing but I have not yet had to trim my cases again past that. I love the ackley shoulder, virtually no case stretch, very good brass life, and a very efficient and mild recoiling round.
If you have any other questions about the AI, need any help with load workup, or fireforming questions send me a PM I'll be happy to help.