i will preface this by saying i am not a law enforcement officer, so i have no idea how my thoughts will integrate with what your department allows and necessity demands.
that said, i'd like to offer the following thoughts.
are you restricted on caliber?
if you're not and you want to go short for handleability / maneuverability with a cartridge that shines in shorter barrels have you considered a 300 blk? Ive been reading quite a bit more recently about its acceptance into military and LE roles.
at close in distances you get a nice extra bit of punch over a short 5.56/223 due to weight pickup and there are company's offering AP rounds for govt use
the barnes Tac-TX 110 grainers are (mostly) barrier blind and capable of defeating Level IIIA body armor even when fired from an 8" SBR at around 2050 fps (mv) retaining 784 ft/lbs at 100 yds
compare that to the new hornady 5.56 "sbr" 75 grainers fired out of an 11.5" barrel @ 2321 fps (MV) retaining 649 ft/lbs at the same distance.
i have a 9" 300blk ar pistol thats just a smidge over 25" in its current configuration. Its handled a variety of factory offerings and a selection of handloads as well in both super and subsonic variety with and without the suppressor attached. even without the can, shooting it (and being around someone shooting it) is a whole lot nicer than being up close and personal with a short 5.56. if you've ever been next to a 11.5" 5.56 with a brake on it on the range you know what i'm talking about.
a sbr built to a similar design would give you a firearm the length of a MP5, carries a ballistic capability similar to an ak47, while still capable of utilizing most standard ar15 magazines & accessories.