Warning. Avianca is VERY aggressive against pax connecting on a Star Alliance ticket, even if its not a 'hidden city' but rather a fully integrated ticket. Last week, we were emphatically refused wheelchair assistance by Avianca on a single ticket CUZ-BOG-IAH ticket that was Avianca to Bogota then UA to Houston. Avianca's position is that, and I quote "Avianca is finish with you" once that AV flight lands in Bogota, even for extremely reasonable requests and for tickets that clearly state that the pax is disabled. If they're willing to do that to a disabled pax, flying on a fully integrated ticket (and fully Star Alliance), they'd probably take your bags to the domestic claims area and leave them there if you tried what you suggest. And quite frankly, I'd question if they'd even check the bag through to your Lufthansa flight even if you bought the whole thing on Avianca.

From my recent experience this week, you also cannot rely on assurances by Avianca staff at the check in airport. Don't think that you'll be treated better if your flying business class either (we were on a full fare business class ticket - not an upgrade ticket) or have Star Alliance status (also true). I would not rely on Avianca to regard Star Alliance as being effective at all. Either way, I seriously doubt that in the event of an IRROPS on the CTG-BOG flight, that Avianca is going to help you at all in that situation. So you'll probably need to account for a long connection in BOG anyway, so you should have time to sort out the recheckin of bags anyway.

Avianca did check our bags all the way through from CUZ to IAH, but I suspect that was only because we were not entering Colombia during our transit stop in Bogota. In your case, you will be in Colombia (not transit only).

My advice...if you do purchase a separate ticket, simply collect the bags in Bogota from domestic baggage reclaim and check in with Lufthansa. That way, you can even fly someone else from CTG to BOG. Which I would also suggest.