Slim stainless shelving would be visually less intrusive than butcher block. Get rid of the OTR ASAP and go with the chimney vent that your architect originally spec'd. You're setting yourself up for a design and functional failure with an OTR. OTR is a big eye intrusion as well as being almost nonfunctional when it comes to venting.

What color are your cabinets and is your microwave vent a direct vent or a recirculating? I ask about the color because Ikea has a microwave cabinet that we used in a barn kitchen and it worked really well. The shelf that holds the microwave was fairly large so we did a little retrofitting to make it work in our situation.
I'm not sure if butcherblock is going to be to heavy or not since it depends on the style of your kitchen and how thick it is.

The pic below gives just one visual of what you could do, design wise, around the frig. I don't know how close the frig is to the stove, or how much width you're dealing with but you may be able to put up at least one cabinet over and one next to the frig and then work from there.

[eclectic kitchen design[(https://www.houzz.com/photos/eclectic-kitchen-ideas-phbr1-bp~t_709~s_2104) by dc metro interior designer Lauren Liess Interiors

Oh my, I thought no one had answered my post (I'm new at this), I don't know if any of you are still around but thanks SO MUCH!!! the contractor is coming in tomorrow to begin and I was awake all night. The entire problem was put on hold while I dealt with my real job and other kitchen issues. Live wire Oak, getting rid of the Microwave has been really on my mind. ALL open shelving that I see anywhere is without such a behemoth and I my hubby and I just use our little one to heat up coffee or a leftover din. when we are exhausted. Your definitive comment gives me will power. On hold is this notion of passing inspection. We can't afford HOOD... no... let me correct that... we were having trouble figure out where/how to vent it without sacrificing other parts of kitchen redo that we liked (LONG story) - so then we discovered the recirculating vent possibilities (and yes, researched on Consumer Reports and realize it does very little) but we have electric stove and figured we could get by for awhile, pass inspection and reconsider things a couple of years after trying out the open shelf thing. Now, of course with everything being so simple, clean, open and airy and nice... I don't want to just stick shelves up so I made it difficult all over again. Annz, thanks for this picture, Its the right feel and I feel better about running shelving right on top of refrigerator as shown. Perfect. I will make plan for shelving tonight - call and triple check if OTR is necessary for passing inspection and go from there. Kitchen cabinets, BTW are natural maple, Floor grey tile. I wanted SS shelves but other half wanted Butcher Block. It still looks nice.

NICE