Bro, the best thing I like about a healthy argument/debate is that it bring out the most useful information which can benefit many besides benefiting the one engaged in the argument.
anyways, I agree that feet are to be placed higher than stock to offer comfort. however If you search on the Internet or notice common behavior, you'll find that most people in order to relax their legs/feet always place them higher and closer together. I would say that it is almost natural behavior to lift our legs up and put them closer. here are a couple of pictures for your convenience:
Now I'm not a medical expert such as your kind self therefore I cannot say anything about it using medical grounds however from what I have observed that the tendency to relaxing legs has always been legs up and close to each other. I could be wrong therefore I am totally open to opinions that are "otherwise".
my second point against this idea is that with feet spread apart, you are in fact adding a pendulum to your bike which is based on the a principle of physics. the greater the distance (where force is being applied) and the point of rotation, the greater the effect of that force in shifting the center of gravity by exerting more kinetic energy (lever action).
now I sure that you'll ask me that why is it those heavy duty harley's haven't thought about it. I would say: dr. Sahib, a harley or a similar class cruise bike is usually pretty heavy and small distance in their case doesn't matter much whereas GS-150 is a minuscule bike (compared to super heavy bikes) so whatever solution we come up with, it has to be modified given the parameters and the constraints posed by our small sized machine.
here is a food for thought: kindly notice where the foot pegs are in relation to the handle bars. you'll get the idea that foot pegs are always designed in relation to the maximum spread of the handle bars. because whenever sudden cornering is concerned, your whole body rocks side ways to balance the bike and the whole body needs to act as a single unit. therefore all extending organs such as hands, shoulders and feet are kept in line.
If you closely at above picture, you'll find that the foldable foot pegs are designed to open inside and inline with the stock foot pegs and collapse backup inline with the crash guard. thats what I call clever engineering.
I hope with these pictures I am able to get my point across. in line always, however if you want to induce better cornering ability at the cost of straight line stability, you can always make your foot pegs placed closer together as in sport/track bikes. But never the other way around.
in my humble opinion, any solution to a given problem should not come at the cost of altering the original equation by introducing another variable.
you are probably right here but in my humble opinion, Suzuki GS-150 looks more like conventional retro bike than anything from the 80s or the 90s era. kindly search for Suzuki GS series bikes built from 1970-1979, you'll find almost all of them look exactly like GS-150. however if you look at Suzuki bikes from 1990 onwards, you'll find considerable changes in their structure which make them look more like sportier versions instead of cruisers.
List of Suzuki Bikes Ever Built
Anyway, the only way to be sure if the lindby highway bars would look good or not on a GS-150 is to try one. if not, I guess....we must resort to some other design.