Why do you want a hybrid or carved? What do you want that your ply does not do for you? And why the 7/8? Why does your ply not give you a loud, punchy tone with loud unamplified volume? I bet your ply is capable of sounding pretty great as well with the right setup. (If you want to play arco for practice or performance, that may be a different matter. But you don't mention any of that.)
I'll repeat what I've said many a time here - like you, I play(ed) mostly bluegrass and oldtime. I wanted to replace my ply 3/4 with what I thought would be a BG cannon - a 7/8 hybrid. And I figured once I got the hybrid, I'd get rid of the ply because who needs 2 basses, right?
While waiting for the hybrid, I put guts on my ply, and I LOVE everything about it for pizz. I regularly get compliments on the tone and comments on the volume (playing outside, people tell me how far away they could hear it.)
So I kept the ply and when I got my hybrid, I set it up for arco and use it almost exclusively for classical, and most of the time in my home. Some day I probably should swap the strings, just to hear how th ehybrid sounds under guts. But for the past couple of years I've been digging having 2 basses set up quite differently.
Other considerations (which we've discussed many a time), the hybrid or carved will be a tad heavier than your ply, and the 7/8 will be a bit larger to haul around. There also is the debate as to whether you would worry about dinging up your pretty new bass, or just accept the marks of wear as part of the territory.
Personally, given your situation, I don't think fully carved will give you anything over the hybrid. And I'm sure the 7/8 hybrid w/ guts would sound amazing. FYI:
Travis Book with the Fabulous Stringdusters plays an Upton 7/8 hybrid with removable neck.
turf3 has it exactly right - get the bass that sounds and feels the best to you, and that is going to make you want to play it more and more!
. My personal opinion, I've NEVER seen a Shen Willow that I didn't think was GORGEOUS. But I've never played/heard one.