I think I'm going to go with Ibex. I decided I'd like my merino short sleeve to have a chest zipper for easier body temperature regulation. The Echo Sport Zip with half zipper from Ibex is 150 g/m^2 and is 100% merino, rather than a merino/synthetic blend. Interestingly, It comes in a color called "Sea Grass/Nickel", which looks identical to the color of my BPL Beartooth Merino hoody. Seems like a winner to me.
I was also considering the Ace Shirt which uses the same weight fabric, but that one is a button up. Perhaps that would be even better for temperature regulation than a half zipper? Although I'm not sure if it would be needed.
I'm also getting the Woolies Boxer from Ibex, which is also 150 g/m^2.
All together it looks like I'll be spending around $120 plus shipping. This will be one expensive experiment to see if I would prefer merino in warm weather instead of synthetic or cotton. I don't like how bad breathability seems to be with synthetic and I don't like how long it takes for cotton to dry. If merino is not too warm in the summer months, it may solve these issues for me.
Any input on these choices before I go for it?
EDIT: Added links to Ibex choices.