I never use TTS-1.   90% of the time I load Native Instruments' Komplete Kontrol, from which I can load my favorite presets from my plugins. 
 
So I would find it very useful if I could assign the Komplete Kontrol as my default instrument.  I bet most people have a plugin instrument that they use more than others, and I doubt the majority would select TTS-1.  
 
Even more useful would be a right click dropdown to "load default instrument"  
 
I recognize that there are many ways around this, using templates, etc., and I use them, but I still think this would be a useful feature.  
 
 

I have created a handful of Track Templates, for precisely what you are posting about.
 
So, rather than trying to do something when inserting tracks - try creating a Track Template for one of these synths - with just a couple of mouse clicks, I can insert Battery 3, a BUNCH of buses, load a particular custom drum kit, AND have it automatically set relative volumes to each kit piece, AND have Sonar add a separate audio track for each kit piece, already configured
 
Track Templates really are that powerful and a breeze to create and use, and I think those would address your issues...
 
Bob Bone
 

Thanks, Bob.  I will learn more about Track Templates.  

The "Add Track" utility should also have a tab for Track Template (in addition to MIDI and Audio).

Now there's a thought!  i like Rockskyl's idea. 
thumbs up for that one!

I agree with the OP.  If there is going to be a default, I should be able to set what that default will be.
 
And yes, I agree that template should be accessible in this dialog too.

I'm glad I posted this, because I am now using Track Templates constantly and they have really improved my workflow enormously.  I'm really impressed.  The Templates remember not only the patch I had loaded, but also the set of windows configurations I create for a synth like Iris 2.   So thank you, Bob Bone!  
 
I also want to add my support to Ricoskyl's idea.  

TigerTheFrog
I'm glad I posted this, because I am now using Track Templates constantly and they have really improved my workflow enormously.  I'm really impressed.  The Templates remember not only the patch I had loaded, but also the set of windows configurations I create for a synth like Iris 2.   So thank you, Bob Bone!  
 
I also want to add my support to Ricoskyl's idea.  

Where I find the MOST help from using Track Templates is with drum kits.  By default, all my drum kits for all my drum synths output to the first two outputs.
 
So anytime I either use a given kit for the first time, whether a stock kit or one I build by picking and choosing individual kit pieces, I ALWAYS customize the kit so that each kit piece gets assigned to its own audio outputs from the drum synth.  I then will insert audio tracks into a track folder called Drums, and have an audio track assigned to each of the kit pieces.  I will then add multiple drum buses, so that I end up with a Drums Master, Toms Bus, Cymbals Bus, Snare Bus, Kick Bus, Parallel Compression Bus - whatever is needed - and then I group the kit piece outputs to go to the appropriate bus.  Those all end up feeding the Drums Master, which itself routes to Master.  I set all outputs to an initial starting point of around -18 dB, toss in 2 midi tracks (1 for dummy click/drone, the other for actual midi to be used for song's drum data), and then save it all off as a Track Template for that particular kit.
 
Over time, I have amassed quite a few of these ready to go drum templates, so that I only have to do all of that work one time per kit, and then I can reuse them forever in different projects afterwards.
 
I also want to mention that I save some time doing the above by loading one of the existing kits into a project, and that gives me all of the audio tracks, midi tracks, the track folder, the buses, and the bus routing assignments, all right off the bat, which saves me HUGE amounts of time.  Then I just replace the kit in the drum synth, get each kit piece routed to separate audio outputs, and then set the audio track inputs accordingly, get levels set, and I'm pretty much ready to go.
 
Bob Bone