I believe if you are just building out the campaign structure that keeping them in the same (grouped) by keyword theme is a stronger approach for the same exact reasons that you have pointed out.
Once you start to generate some significant data in there, you can always pull those exact match keywords out and place them in their own adgroup for further testing if you will. Intent could potentially be different but without some level of data to review, it would be hard to make the case.
I would go the route as you have outlined and go from there.