Multi-Use Inevitable Catastrophe Building

Good Day Permies!

It's been awhile since I've posted here...but I guess that's life.  I got duped into getting ducks this spring...and since they don't like the chicken coop I guess I'm building a duck coop.  Now because I'm a moron and like to overcomplicate things (and because I'm not in love with our chicken coop in the first place, as it just gave me a 9" gash down my back and ripped one of my favorite t-shirts...) I've decided to just rebuild the chicken coop too.  One of our future projects was to build a greenhouse...and since our yard is large, but not country livin' large it's now getting integrated into this building as well.  The greenhouse was going to be about 5' from the foul yard anyways...so why not connect them (start ominous music).  So, I've posted my plans below to get some feedback as to how dumb of an idea this all is before I get started.  
Few key details:
We will have 7 chickens & 4 ducks (however I've sized it to hold around 18 total birds...)  (the ducks are runners & khaki's)
I already have a bunch of 2"x4" and 2"x6" and sliding glass doors (for windows)
I already have a bunch or metal roofing material
I already have the 55 gallon drums
The greenhouse will step down a couple feet into the ground (hoping for a net of 2' down)
I have access to a small backhoe for the groundwork

General plan:
Overall the building will be 8'W x 23-24'L x 10'T.  The greenhouse will have 2 permanent in ground planters for something like a fig or pomegranate...that can freeze, but maybe doesn't like -30F.  I do not plan on heating the greenhouse, nor do I expect the birds to keep it warm enough in the winter...I'm just hoping it's warmer than outside...and that some plants that I can't grow outside will be ok in there.  The greenhouse will primarily be used for seed starting, and frost protection of planters in the early spring / late fall.  All walls except the south wall will be insulated, with no glass.  The roof will overhang quite a bit to help with summer overheating.  In the winter the air vents will connect to the foul side of the building, but be closed to the outside.  In the summer all the vents will open, there are low vents and high vents to encourage airflow, and I will probably put an exhaust fan on one of the high side vents.  The door to the outside may end up being an insulated storm door that can open for airflow as well.
I'm planning on catching the rain water of the single pitched roof and running it through 1" PVC pipe into a rain barrel/heat retention system inside the greenhouse.  Since the door height is about the same as the gutter height, and I want the rain barrels on the back wall, I've designed a little PVC collection system and routed it under the floor (schematic attached as well).
The bird side of this catastrophe will have pretty standard coop stuff, combined with some duck stuff.  The floor will be slightly elevated, and simple to allow for deep straw bedding.  There is a cleanout door under the nesting boxes that can be lifted from the outside to provide a 2'T x 4'W opening to push out the spent bedding.  2 rows of elevated nesting boxes for the chickens, and a triple roosting bar will provide the ladies all the room they need for their general happiness.  The ducks on the other hand will have a small attached sleeping area, their own nesting box, and what I've found called the "duck dipper" (see photo below, this was taken from Carolina Coops and is in no way mine, nor my idea...I just like it).  Also sorry the plans have an error in them...the duck nesting box was left off...it's inbetween the duck dipper and the duck sleeping area.  I've read ducks are unreliable at nesting boxes anyways...

If you have any thought please let me know!

Hi Colter,
You have just realized why barns are so popular for farmers and homesteaders... gets everything under one roof :) About your plan, I think overall it looks pretty good.

There are only two things I would ask about. One is the water system. Forgive me if you were already planning this, but some of the text on your plan is hard to read and it appears you are planning to put it outside. I would try to fit the water system inside the envelope of the building. This will lower the chance of the water freezing and causing problems. Even if you were in a hot climate, it would keep the water cooler. And either way, it might extend the life a little not having the plastic exposed to the sun so much. And if its on the greenhouse side, it can provide some heat storage.

Second is the doors. It appears like you were planning to use 36" doors for everything? Again, forgive me if I'm wrong. But with a deep litter system for your birds, I'm assuming you will want to use a wheelbarrow on occasion. A wheel barrow might also come in handy on the greenhouse side to carry soil and stuff back and forth. 36" would be pretty tight for some wheel barrrows to go through. I would want to use a double door (or build one at least 4' wide) personally. If that is not an option, then make sure your wheelbarrow will fit. Or anything else you might want to get through. 36" is tight for carrying haybales through or chicken boxes or quite a few things actually. Even though you can sometimes get things through, it is much easier to have some wiggle room.

***Edit***
PS I made the mistake in my greenhouse of not thinking about the base of the doorway. I use 6x6 beams all the way around, and realized that was quite a bump for the wheelbarrow to go over. I banked some dirt, so it wasn't too bad, but something to think about.