There shouldn't be any additional workflow issues if you shoot .mov files. If you shoot AVCHD then you'd have to transcode the .mts files I think.
I'm not sure if there is an equivalent to John Hope's old Cinema profile. I normally set the GH3 fairly flat and grade in post. The problem I had wasn't with the look of the Canon files except for how it dealt with highlights. I do a lot of outdoor weddings and I got tired of Wedding dresses blowing out. I've tried the old Cinema profile as well as his new Lightform profiles, ProLost, and VisionColor and VisionTech profiles and none of them gave me a great looking file in contrasty situations. I've shot the GH3 in conditions that I KNOW would've been problematic with my 5D3 or 5D2 but the GH3 performed excellently.
Dynamic range isn't the only determining factor in why I think this camera is so good. I've had plenty of experience with Canon cameras. I've owned the 5D3, 5D2, 60D and T2i and none of them gave me the quality image that the GH3 does. The thing that I love with the 5Ds is the look of the full frame sensor. Now that Metabones is going to release a M4/3 adapter that brings the full frame look to that small sensor it basically removes the main reason why I would stick with my Canon bodies. I get better quality and more speed out of my already excellent Canon L glass. The GH3 is also less than half the price of the 5D3.
Seems like you might be best off borrowing or renting a GH3 and seeing if you can dial in the profile to intercut with the Cinema profile on your Canons. I'm a bit hesitant with some of the higher bitrate GH2 hacks as they aren't quite as stable. As a wedding filmmaker I can't have cameras crashing on me in the midst of a wedding. One option is the FilmConvert app. You could use it to grade your GH2 footage and Canon footage to a similar film stock profile.