Admittedly, I'm not very well versed on my Berliner Weisse history, but I would guess that back in the 15-18th centuries the sour mash would have been more likely than using a pure strain of lactobacillus delbrueckii.
I recently used a sour mash technique on a BW, and it scored a 46 in a BJCP sanctioned competition. I did a single decoction mash, sparged as normal, then transferred the wort to my sanitized 5 gallon jug cooler, and pitched about 4 ounces of grain once the temperature reached 125. 20 hours later (the temp dropped to 95), I briefly brought the temp of the wort up to 205 (yep, no boil), then cooled to 65 and pitched a neutral ale and various brett cultures. I think the initial 125 degrees pitch rate and 20 hours allowed for the perfect amount of sourness.
I thought the beer was really good even young, but really hit it's stride at about 6 months when the slight brett aroma/flavor started to appear.
One trick I've figured out with sour mashes is to fill the cooler with 4.5 gallons of wort, and then top off with a 2 liter bottle of carbonated water before quickly closing the lid. The carbonated water releases CO2, which seems to do a really good job of purging the headspace of O2, keeping oxygen friendly bacteria from producing off-flavors. I've done this technique a few times and I've never had a problem with bad smelling mashes. I wouldn't say the mash smells great (has a slight vegetal/cooked corn smell), but it doesn't smell awful either.
I would eliminate the carapils, however, if you're trying to stay traditional. At the very least, I would cut it down to 4 or 8 ounces at the most. I would guess the extra body would take away from the perceived dryness that is essential to the style and, in my opinion, makes the beer so refreshing.