It's probably too late, but I've been researching the same thing. I think you're best bet would be to go with brett. C. if you're going traditional. It's on the milder end of the brett. funk scale. If you innoculate from the beginning, I think you may end up with overattenuated beer, which would be out of style for an old ale. What I think I would do, and I'm currently planning on it with an old ale I have in primary right now, is to separately condition 1 gallon of it in secondary with brett. c. and let that ferment out. Let the other 4 gallons age as is, in parallel. Come bottling/kegging time, pasteurize the brett. c. infected portion, and blend it back in to taste, and continue as normal. Alternatively, I may just keep that infected portion for some other future batch instead, who knows. But I think blending is the way to go so you can avoid overdoing it or overattentuating it.