I don't think you'd need a 1 grade, (there is no F or G at A-level so it'd represent a sub-E standard, probably meaning everyone passes) or an extra grade around the C. (the reason this was done is quite specific to GCSE I think) 1-7 would probably work fine. (with the extra grades for B+/A+ and A*+) But I wouldn't be surprised if they just went for 1-9 so there's less confusion. (then offers like 988 would probably be just around the corner for the very top courses)
I would speculate the main reason this is done is a) to make deflation easier and less disruptive (not 100% sure it'll work out this way though) and b) they were probably planning to do it eventually when they made GCSEs 9-1. (just like the GCSE was the first to get the A* grade)
Actually thinking about it, isn't IB already 1-7?