My view is somewhat different regarding perceived wheel gap, which is why once a owner does upsize (plus 2" for a 17" to 19" conversion) they often feel the need to lower the vehicle afterwards.
Reason is the relationship of sidewall height (shorter sidewall of the 19" for example) to the wheel gap , wheel gap stays the same given proper tire sizing/rolling diameter. But because of the change in relationship or ratio of sidewall height to gap, the perception is of greater wheel gap with larger diameter wheel. It's a common visual issue with modded cars at least (sport coupes, sport sedans, roadsters).
Regardless I do hear what you are saying when it comes to the CX-5. And to me the stock 19's look far better on the vehicle than any other stock wheel (and using stock springs, retain that well-engineered comfy ride/handling combo). TexanCX5 pictures really show that, especially when he put 19's (yaah man) on front, 17's on rear (eeewww).