First off, the relative size of the drains is different, but that is generally NOT going to be either something that matters for "code compliance" or any expensive retrofit. Drain lines commonly have adapters to allow smaller or larger traps to fit the sink.
Secondly I have seen MANY manufacturers offer very nice "laundry sinks in cabinets" that work very well as powder room or similar here is just one example: Vanity Laundry Sink - 31-inch Cabinet with Single Bowl - Stufurhome
I have seen even "jetted sinks" that use the same technology as whirlpools to sort of "hand wash" delicates. MTI MTI Jentle Jet Jetted Laundry Sink 25" x 22" x 11 1/2" - MTLS110J by QualityBath.com
Many nice options: Deca Laundry Sink - UL110 by QualityBath.com
Kohler has a whole line of compact utility sinks that can be used as a combo in a lav or laundry, plus they make a very nice "remote drain" strainer assembly that keeps your hands out of the mucky water. I saw folks put these in to help clean their pets and such: Kohler K-6655-1U-0 PARK FALLS Park Falls Undercounter Utility Sink White*-*eFaucets.com