Sure. But I think the issue of having to manage both of those synths and MIDI channels separately from that point forward is a significant barrier to a good workflow. Needing to remember to arm both channels and/or copy linked clips is a hassle. Then if you want to drag them around, you have to select both.
Probably the best workflow Sonar offers for this is to put the synths you want to layer within a track folder, so that you can click just 1 button to arm all the tracks or to enable input echo, and to group the clips as soon as they are recorded so that future drag/drop/slip-edit functions operate across all copies of the clip. And if you want any effects to act on the layered sound you'll have to route them all to a common bus and apply the FX there (though this may no longer be the case after the "Track to Track Routing" feature gets delivered).
(Maybe there's a way to mimic some of that via Quick Groups but if I'm being honest I never really got that feature working, and I don't know if it even still exists.)