I've been trying to figure out what it is you have a problem with as it does not make any sense to me, and possibly most of the others around here so therefore no answers.
We EXPECT when we change our hardware set up that older projects will need a few minutes of TLC to bring them up to date on the new system. This doesn't take much time really. So not sure what it is your mad about.
I have over time changed my system, my interfaces, my controllers and my computers a dozen or more times. I'm always happily upgrading.
Sonar is pretty smart and warns me of some of the changes and even re assigns some stuff without issue.
The most troublesome has been any old projects from one system that the Master is set to my SPDIF instead of 1/2 resulting in playback silence and a few minutes of pondering until I remember that fact. Otherwise all works as expected.
In preferences I make sure my 3 midi input devices are checked and ready to use.. I really don't care where they are on the list. Why would that matter? They show clearly on the midi track input list so I just select the controller I want when I'm recording midi. a 3 second task.
I do not select any midi device outputs as mostly I'm not driving any outboard midi gear and if you don't select a device Sonar will automatic insert TTS_1 and populate all 16 tracks when you open any midi file. A huge timesaver for me.
If I want to hook up some old midi hardware it takes a half a minute to select my Scarlett midi output.
NOBODY uses on board wavetable synths unless they are tone deaf. Sonar should totally remove that as an option, it would keep new users out of trouble.
Now if your talking about midi track outputs those will always stay assigned to the VST instrument they originally used unless that VST is no longer installed. You'll get warnings when you open that project and they will show greyed out so easy to find a newer, better replacement. Sonar will ussually re assign midi tracks to the last used VST. Supper easy to change.
I open older projects almost daily as I upgrade my backing tracks using newer better VST instruments. Midi files I made on a 1985 Atari 1040ST still open and will play. But I don't expect the Bass patch I used in 1985 to be correct. A little TLC to each project and 15 minutes later using track templates I've got a whole new upgraded sound.