Hypothetically yes, the Velox plates are relatively symmetrical and rotating to achieve additional caster looks possible.
However after looking at the trigonometry you're basically ending up with
instead of 100% camber adjustment a ratio of about 1:1.7 camber:caster gain. These aren't real numbers but ballpark you'd go from gaining say 2 degrees of camber to just 1.2 degrees while picking up 1.7 degrees of caster.
Most people feel that this car has adequate caster from the factory, it's not a Miata or S2k (and I presume Honda FWD cars) that comes with low caster (5 degrees or less I believe) and benefits by increasing the caster. OE comes to about 6 degrees and the Raceseng plates allow for an additional degree approximately.
Contrary to the Miata and S2k, with a Macpherson strut front in this car has a stronger need for static negative camber because it doesn't gain camber under compression like the double wishbone suspension cars mentioned above.
For reference, my camber plates give me -2.5 degrees, the last event I ran I had them maxed out at -3.6 degrees of camber per side (I also have camber bolts), and I believe my car would have been better if I had more camber in it. There's no way I'm even going to think about sacrificing camber for caster at this point.
I've read it's a common tradeoff on Miata and S2k's to balance your caster/camber, but they have a completely different suspension design that has different strengths and weaknesses from the FR-S/BRZ.
tl;dr The 86 with an additional -2 degrees of camber over stock will be significantly better (more grip) than the 86 with an additional 2 degrees of caster. By rotating the plates you are sacrificing camber for caster, likely to the point where you are negatively affecting your performance by not having enough camber for your front tires to operate properly during cornering.