Agreed on all counts. The thing about Keldon, though, is that for the Spurs specifically his ability to finish at the rim (while obviously useful to an extent) is not a need of urgency. Due to the team's current composition (I'm skeptical the FO will blow it up until at least next season) the lanes and paint will be much too clogged for Keldon to go to work using his body, and given that we already have a lot of non-shooting players that already clog the paint to a degree, adding a non-shooting SG/SF (it's irrelevant if Keldon plays the 2 or 3 since DeMar will occupy the other guard position) is a recipe for disaster. Teams will easily dare the Spurs to shoot from outside. Keldon going with the bench lineup isn't much better in this aspect either (even though ideally he should start for his defense alone in place of the POS midget); White is more of a pass-first PG and Rudy doesn't trust his shot nowadays for some reason, and obviously Jakob "3pt shot" Poeltl doesn't space the floor in the slightest.
I could see a future post-blowup where we start DJ-Lonnie-Keldon-Luka-Poeltl, for example, and that could work if both Lonnie and Luka are willing to be volume shooters. But with the way this team is currently constructed, we just can't afford more minutes to non-shooters who aren't difference makers in other areas, or at least that's what I see.