Fermenting fruit pure on souring strains

Just a couple observations. Don't use Pedio w/o Brett, it throws off tons of Diacetyl that the Brett cleans up, and w/o it you'll have sour fig juice with popcorn butter; maybe just use the Lacto since there won't be any hops in the puree to inhibit it. The other thing is that the yeast (Brett) might get used to the simpler sugars from the fruits and then not want to go for the more complex sugars in the wort. Just a thought, and I could be wrong. If I am wrong, go for it, sounds like it would work if you were able to get it to still want the complex malt sugars.

 

I have done this a few times. I suggest letting the beer age a while on the bugs/wild yeast for a period by itself. I find adding the fruit in the last 2-4 months before bottling gives the best fruit flavors, allows the sugars to be eaten, and allows the bugs to mingle with the fruit.

On sour beers I want a lot of fruit flavor I have added fruit in 2 stages, once with an estimated 4-6 months left and a second time with 2-3 months left before bottling. Here are some pics.

 

I might be a little confused, but it sounds like you are interested in blending various styles and clean/wild brews

From what you are describing, adding wild brewed beer to regular beer there are a couple of concerns I would have. The first is there are a lot of sugars left in the regular beer that will be eaten by the wild yeast/bugs. You would either need to consume quickly or tailor how much priming sugar you add. Otherwise beware of bottle bombs.
The other thing is sour beers take a while to develop and can go through weird phases (especially young). I would be worried that once you blend the two beers the wild bugs will eat the left over sugars and give an awkward flavor that only time could heal.

However, I know commercially what you are describing has been done (3 Philosophers, Transatlantic Kriek). If possible you could filter out the wild bugs and some how stop them from eating anything else. Others might have experience with this and can point you in a better direction.

here is what I have done in the beers pictured above.

The top picture is of a sour quad. The large carboy is 5 gallons with no fruit, the one gallon is the same beer with 2 lbs of cherry. After 3 months on cherries I blended a little bit of the regular with the cherry version then bottled each version. From brew to bottle date was about 1 year.

The other beers are of 6 gallons of a pale session sour (only 3.5%ABV). After about 6 months I put about one gallon of the sour on various fruit (about 1.5 lbs), after 3 months I transferred the 1 gallon containers of fruit sour to another 1 gallon container containing more fruit. I just bottled these last week, brew to bottle is about 14 months.

 

I have never done it, but I am not sure you want to heat your beer up to pasteurizing temperature. At this temp you would be very close to the boiling point of alcohol, and I would guess there could be some damage to your beer.

just doing a quick search here are some suggestions

http://www.thebrewingnetwork.com/forum/viewtopic.php?f=&t=21672 (do this just to the wild batch, involves a dual counter flow setup)

http://www.pasteurizers.info/2009/06/pasteurizing-homebrew-to-increase-shelf.html (note: your beer would need to be fully carbed before doing this method)

since you are new, but interested in brewing some sours what I would suggest is brewing a normal clean beer that would be good for souring (Belgian Pale Ale, Quad, American wheat ale, etc). Then take 1 gallon of this beer and add in dregs/culture. Let this beer sit for a LONG time, like 9 months to a year, tasting every 3 months or so. This will give you an idea on what to expect. Towards the end, when you think the beer is tasting about how you want for bottling you can add some fruit you think will compliment the flavor of the beer. After a month or two, start tasting again to gauge when to bottle. You might want to add a little bit of yeast for bottling. Doing this will help you learn a little more about the process.

and by near default when talking about brewing wild brews, check out this guy's blog:

http://www.themadfermentationist.com/