No reason why it shouldn't work although there is a larger offset on the AP1 which might not blend so well in the AP2s. It is certainly often done with CB/MB and i've even seen a set of AP2/CB/MB - looked a bit odd tbh and that's something to consider as the AP1 and 2 look a bit different. 

I read some where that Zach Johnston carries AP1 long iron or 2 depending on the course he's playing

I have a combo set after a custom fitting. My set is 4-7 Ap1 and 8-W Ap2 and I love the set as it gives you the best of both worlds.. I really love the Ap2s but would probably struggle to get consistency with the longer irons and the Ap1s are a little more forgiving.  One thing to be careful of is the lofts as Ap2s are not as strong as the Ap1s, but as I did a custom fit I cranked up the loft on the Ap2s to make them blend in perfectly.  As for the clubs looking different in the bag, that doesn't bother me at all - I like the look of both clubs.  I hope this helps, Let us know what you decide to do.