I have an Allez sprint, which has dropped seatstays and a w i d e aero post. Here's a list of stuff I'd like to mount:

Frame pump (currently under top tube)
Headlight (mounted on bar tops)
Front camera (can mount on other side of bars)
Taillight (the one I bought that claimed compatibility with aero posts was not so)
Rear camera(I think a saddle rail mount or SWAT mount would work, unless someone can find an aero post gopro mount)
bag (for tube, multitool, tire levers, patch kit, currently using a saddle bag)
2 water bottles (ie no water bottle caddies)

A few issues: a saddle bag means that a SWAT mount or rail mount don't work for the rear camera. I'm open to alternatives that are not "just put it in your pocket" because I hate putting things in my pockets and definitely don't want to deal with falling on hard plastic/metal.

Also I'm looking for rear lights that are confirmed to work *well* with a venge or Allez Sprint aero post. The one I bought is so stretched out that it doesn't clip properly. There's nowhere else to put it because the dropped stays mean there's no space between the brake bridge and the seat tube.

Thanks

Did you check this thread?
bikeforums.net/electronics-lighting-gadgets/1126857-minoura-spacer-light-gadget-mount-di-light-fender-hole-mount.html

For Aero-seatpost i recommend Cateye or Specialized:
cateye.com/intl/products/safety_lights/TL-LD720-R/
cateye.com/intl/products/parts/5447040/
specialized.com/us/en/flux-expert-tail-light-seatpost-mount/p/132561?color=219819-132561
specialized.com/us/en/flux-expert-tail-light/p/131113

Sigh. Can't say I'm excited to spend $70 (cateye x3 needs a $10 adapter for aero posts) for a basic LED that blinks. I have a $10 light that performs plenty well for me.

I've decided that I'm going to go with a top tube (gas tank) bag instead of my saddle bag. Those aren't cheap either but one bonus is that they're slightly bigger and more accessible so I may be able to put my phone in there.

This will mean I can get a rail mount for my rear camera. If anyone could point me to a cheap rear light that actually fits an aero post, that would be great. EDIT: What about the giant numen plus aero? It looks pretty sweet too.

You didn't name any budget before, so i'd show you the best light Maybe it's time to stepu upt with your safety?
You can also mount nearly any other Cateye Taillight on the universal cateye rear mount.
Cateye-LD620-R-Rapid-Micro-USB-Recharge-Small-Bright-City-Bike-Rear-Tail-Light/292466861128

If you look on Amazon there are plenty of Cateye X3 clones that are ~ $18 and since most of those are using rubber straps I can't see why one of those wouldn't work on an aero seat post. There is also one called the Nkomax that is designed to be mounted on the seat rails. Of course if your plan is to mount a camera to the rear rails of your seat you likely wouldn't want one of those ...unless you don't have a camera yet and if so you could consider the Fly6 HD camera and rear light all in one. There is an aero adapter for the Fly6 but might be hard to find.

Something else that might interest you; You might want to check out some of the different aero options they have on Amazon for storing equipment. I only mention this because you mentioned still mounting a frame pump to your bike under the top tube. That is so old school and as everyone knows it really does take away from the clean look of your bike. You might consider something like this. Should be big enough to fit a small pump or CO2 inflator and a tube and tire levers. I was actually thinking of going with something like this myself so I could get rid of the frame bag I now use that sits between my top, head and down tube. I even thought that maybe I might be able to use one on the rear of the seat tube behind where the tire comes down...heck maybe it might even work on front of the head tube. A lot depends on the bike and the different cable setups as to what works. Scroll down the pages on the Amazon link and you'll see even more options. Every time you click on something new once again scroll down the page and you see even more options. When I see something I like I just put it in my cart while I'm browsing. I can always delete or move to save if I'm not buying at the time.
( Edit; you might want to check out this thread on adapting a Cygolite Hotshot to an aero seat post. )