You can place flare trip mines while capping a point just as easily as you can just cap the point. All it takes is pressing 1 extra hotkey. People place mines and demo charges all the time while they cap points, flare trip mines are placed just as easily.
Once you get the hang of frequently placing flare trip mines, you will probably find yourself thinking "I should place some flare trip mines!" even when you are not capping a point.
It's just something that takes some getting used to. Abilities that are fine should not be changed just because players can't be arsed to pour some extra APM in their play. This is not starcraft, you are not constantly maxed out on APM.
I think we both agree using trip wire flares is a matter of how good a player's APM and micro is. You can either manage to fit trip wire flares into your micro or not. I am glad you are able to integrate the mines into your gameplay (and I will have to experiment to see if I can as well) but I believe it is safe to say you are the anomaly and not the norm in this regard. My suggestion is to merely increase the ease of use of the mines so that the community at large is better able to take advantage of them.