Is there a way  (rapture pro?) to combine sampled instruments into one midi instrument or track? I frequently use standard combinations in orchestration, and would like to be able to call them quickly, and also save computing power. As an example, a flute and violin double with piccolo an octave up.  It'd be nice just to pull that up as one instrument.

I will be boring people with this, putting it often as suggestion - but here it is:
http://ddmf.eu made Metaplugin which can host just about any number of synths and effects.
 
And combined with vst midi plugins between synths you can start to be creative as ever.
Combine different arpeggiators with synths and I don't know what - save as a preset.
 
And since a midi out also, you can feed other tracks in Sonar from that instance too.
 
Need a range of midi plugins for free: http://thepiz.org/plugins/?p=pizmidi
Download links to the right sidepanel.
 
But don't forget about track templates in Sonar, very useful for what you ask for. They store both plugins/synths, tracks, busses and routing to insert in a sec from menu.
 
 

I think I may have answered my own question with Rapture Pro. You can load as many as 6 sampled instruments in each element of Rapture Pro. It owrks, but i really haven't gotten a good result yet. However, there are enough tools to make something work. 
 
Garritan's Personal Orchestra does what i want, but since I already have Rapture Pro, ......

I think Cake might have a look at Arturia and AnalogLab implementation.
 
You have two modes - one working with a single instrument - and scenes(or what they called it) that could layer any way you like.
 
Their selection and filtering was good too - edit own presets into categories, favourite star marking etc.
And this over a range of 5-6 synths or whatever their collection were.
 
Didn't see RP, but the filtering might be there., but saw a comment that cross instrument were not, somewhere.