I'm sure it's the brugmansia that has rooted. You can pot the brug. Keeping it warm and in a well lit area is good. It can go outside when it warms up. Plumerias take a long time to root. They are also rooted differently then most other plants. They need bottom heat and a very well draining potting medium that is allowed to dry out completely. You should take a look at the GW plumeria forum to see how it's done.

Of course you can have 2 units tied into 1 duct system. As to your actual question, i'll answer it. You will need to either manually or mechanically block off the unit not being used...Fof instance, install the gas furnace facing the existing heat pump etc, then slide a rigid baffle in front of the heat pump, blocking any pass through air flow when using the gas furnace...lol, simple as moving one baffle incorporated into the supply plenum. 2 separate T stats, separate power supplies, same existing duct system, supply and return. I never did like the way 98% of people ask you more questions than you ask them.....Why, Why, Why.....dunno "Why" they need to know Why, just answer the question OP posted, lol.

Before PETA comes after me, it's zinc. :D It's from a 19th century boucherie chevaline or horse butcher shop in France. I purchased from a San Francisco antique store's website (The Butler and the Chef). Here's a photo of it from their website: I first saw one in the back of Veranda or Southern Accents. Called the antique store in Atlanta - 6K. :( I hunted and hunted and hunted until I found one semi-affordable without any damage (they have holes much of the time). It is the most expensive accessory I have ever purchased. We live in a horse community, so it's fitting.....and I counted it as a Christmas/Anniversary present. I can justify any purchase. lol At its new home: Someone suggested I buy more to go over the other doors. lol Don't think so. Less is more sometimes. imo, it's balanced out by the things above FP on other end of room. If you really want one, 1st dibs usually has several on their website. The first one is not a bad price - less than I paid - but it has some damage. The 6500 one on the red horseshoe is actually the one I saw in the magazine. I see they still haven't sold (and that was 2 years ago). I love the patina/paint on that one. :( Here is a link that might be useful: Zinc horse heads

ugggh. foosball, allow me to skip all this and answer your original question! YES. If you have power in that box that "continues on to an outlet", that means you've got a hot feed and a neutral in there, which are what you need. To achieve this: Inside the switch box, remove the ALWAYS HOT wire from the already-working switch. Add a wirenut and two pigtails - one going to the existing switch, the other going to the COMMON (black) screw on the 3-way switch. There should already be a wirenut or other splice attaching the incoming neutral and the outlet neutral. Add the white wire from your 12/3 to that splice. Connect the black and red wires of the 12/3 to the remaining terminals of the 3-way switch. Inside the ceiling fixture where you've run the 12/3 to: Connect your fixture's white wire to the white wire of the 12/3. There must be another piece of 12/3 that goes from the fixture to the remote 3-way switch. This cable's white wire should be permanently relabeled hot (use a black sharpie) and connected to the fixture's black wire. At the remote 3-way, relabel the white wire and attach it to the COMMON terminal. Attach the black and red wires to the remaining terminals.