How well does any amp fit in a mix? Depends on the sound of the amp, the songs arrangement and the skills of the mixer....
No different with the Kemper. There are literally THOUSANDS of different profiles available for free, tweakable to beyond recognition. If you can't get the guitars to sit in the mix, it ain't the Kempers fault.
With a decent profile, the Kemper sounds like a well-mic'd amp. It sits in the mix just as well as a real amp that has been properly mic'd up 
+1 It entirely depends on the profile.
Welcome!
It also depends on the skills of the one who is mixing.
I have a bundle of profiles from Nashville cat Michael Britt that have a re-occurring theme of full bottom and warm highs that I use often for the rhythm guitar track. I have another bundle of all Marshall profiles I bought from Top Jimi that have a much thinner bottom but, on the other end, these bright slicing highs and these lovely even order harmonics we all desire that are perfect for the lead track to stand out of the mix. Less gain, rhythm pickup, chords below the 9th fret, Michael Britt profile. Top Jimi Profile, more gain, lead pickup, above 12th fret, single notes. It almost mixes itself.
Yep. A tone that sound spectacular alone or with a certain combination of instruments can sound completely wrong in a different mix.
While I understand your concern, I'd turn it upside-down: a good sound engineer can tweak any sound till it properly sits in a mix.
And remember that bass tone is a huge part of guitar tone in a mix 
Well if a guitar has been recorded well in the first place it should just be tweaking the eq to hopefully carve out some space for the vocals?
With recording and mixing my general rule is less is more and always cut frequencies before you start boosting them. The Kemper fits very well into a mix but my advice would be to record a lot of the parts with the spdif and then reamp so you can adjust them. I'm not a fan of recording guitar parts with reverb because it can be so hit and miss.... and once reverb is recorded into a part trying to get rid of it is a nightmare.
But for tone the Kemper with a decent profile more than fits the bill for the style of music you want to play
With a decent profile, the Kemper sounds like a well-mic'd amp. It sits in the mix just as well as a real amp that has been properly mic'd up
+1
It will sit in a mix just like a real amp.
castmemberzack, welcome to the forum.
Listen to hundreds of songs and videos of bands and producers using kempers on released albums in the link below.
Scroll down this link and you'll hear what it can do.
http://www.wikpa.org/Various_stuff
Surely it depends on the mix?
