Sous Vide Pork Butt Char Siew (Chinese BBQ)
If you're concerned about safety, then 135 degrees is definitely not "safe". The FDA recommends pork be cooked to 145 degrees farenheit, and due to the law of thermodynamics your pork will never reach that temperature. You'd need to make sure that your broiling would finish cooking your pork to a safe temperature.  Of course, the FDA guidelines always err on the side of caution, but it all depends on what you're looking for when you mean "safe" :).  However, according to this site (http://www.sousvidesupreme.com/en-us/sousvide_cookingtemperatures.htm), your alloted time seems safe. The nice thing about sous vide is, as long as there are no hotspots, your meat will only ever reach the temperature of the water (135), and so won't overcook, so you can err on the side of caution

Another concern I have is, at this temperature the fat will not be able to render out properly at this temperature/time. Not a huge problem, but perhaps a problem nonetheless.

Lastly, the best part of char siu is the wonderful smokey flavour and the glaze you get from grilling it for an extended period and basting repeatedly. I'm not sure how successful doing this at the end with just a broiler would be.

However, I will say I've never tried making char-siu this way, and these thoughts are only based on my own experience, so I would be very interested to hear how this turns out!