Even though this might be nice, I find that I will most likely make changes in the volume level anyway, regardless of where the preset level would be set. For example, levels can vary greatly within the various sources such as TV with big volume differences between stations. Even DVD's vary quite a bit, requiring level adjustment. I just do not have a set level which I use for each of the various sources that I would not make a change in for any number of reasons. Chances are good that I'm going to pick up the remote and make a volume change for any number of reasons including environmental factors such as "Turn that down, it's too loud!" So, point being- I'm probably gonna make a change anyway, so no big deal for me.
In regards to sub level changes, once I set the trim and crossovers, I rarely have had reason to change the sub level for music or movies. Maybe I'm just lucky. On the rare occasions I do, it only takes a few seconds and it's done. I could see this being a problem if you are constantly making adjustments in sub levels- an easy to access sub trim button on the remote could be handy. For me, these are very minor annoyances and are easy to live with.