I have, use on occasion and really like, an OSOE Shotgun Micro Rig, but I'm not sure I would take the time or trouble to toss it on in a HD situation where I live. Now if we started having home invasions by armed groups of two to five thugs...a situation not uncommon in some places OCONUS and a few locations near the southern border, I might reconsider, although in that case I'd likely go for a plate carrier set up for shotgun instead...just as fast to throw on and adds ballistic protection as well...and for those who say 'carbine', understand that in many locales OCONUS as well in some here in the states, the shotgun is much easier to own than any self loading rifle or carbine.
While I freely admit to not being a fan of sidesaddles, the facts are that one is most likely going to have to fight with whatever is in, or on the gun when you grab it...that includes a good light, hopefully.