We are adding some built ins to create an office space on our first floor. The front face of one base cabinet will bisect one of two wall-mounted HVAC registers in the room (see pic). The register pictured is at the end of the duct line and mounted in an exterior wall. The other register in the room is upstream on the same duct. The basement in this area of the house is finished without easy access to redo the ducting from underneath. I am trying to think through different ways to manage it, ideally with minimal drywall or floor work. Here are the ideas I’ve come up with so far:

1. - Close off half the vent with metal ducting. I could then cut the register faceplate in half with the cabinet butted against it. This option is easiest but may not be code compliant.
2. - Add an extended stile to the cabinet so it creates a cavity where it joins the wall, then create an angular box directing airflow from half the original vent into a narrow vent I would cut vertically into the extended stile where the cabinet meets the wall. The downside here is I’m not sure how the aesthetic of the cabinet will look with a vent cut vertically into the extended stile (vs. a horizontal vent in a toe kick, which is not an option in our cabinet designs).
3. - Add a flush face surface vent into the butcher block countertop to manage the airflow from the half of the vent that is blocked.
4. - Hire a professional to move the vent either towards the ceiling or into the floor. Downside is additional drywall or floor work.

I’m leaning towards #1, but wanted to get ideas from others. I don’t think shutting off half of a single HVAC register at the end of a duct will cause a material issue in terms of airflow to the roomor back pressure on the blower motor, but alternative views are welcome! Appreciate any feedback the interwebz is willing to offer.