@LI-er
You have so much patience in answering everyone. The level of negativity here is baffling.
Your gear has no effect on anyone else so why are they so worked up?
You made some good points, let's discuss?
The black rubber keeper for your main regulator is not needed if you put a clip on the regulator itself.
This is easy to dive with and clip when not needed.
There are hundreds of videos on YouTube when you search "regulator bolt snap"
Andy Davis has a nice tutorial:
How to Make a Sidemount Break Away Hose Connector
There are different ways of doing it
The little red clip for the computer can just be on the computer. A better place for computers is the foot pocket in the fin. The computer will be somewhat protected from jostling and rough handling. Some people have bungee fin straps so the little red clip can snap right on it or you can loop the computer bungee on the strap. It also works well for freediving since the computer(depth gauge) is already with the fin and the mask can go in the other fin. If you have an arm slate, it can go in the fin with the computer.
Can you think of a way to get rid of those retractor thingies?
The surface marker setup only really needs the two clips. Double enders will give you more options, in my opinion.
Some people have a finger spool connected to the surface marker. They have 100ft of line and only need one piece of brass.
The surface marker does not need a dedicated clip, but if you feel like you need one, then a double ender gives more options.
The Mini SPG is a backup for a tank pod?
Why have it at all? It is just another failure point and another hose for no reason. Your emergency procedure should stay the same as all other recreational divers: No gauge = abort dive. What does your gas planning look like?
Most modern (free) software, have a gas consumption calculator based on your surface air consumption, tank size and tank starting pressure. Even without an app, you should know your turn-around pressure and time.
I see no reason to add another hose. And you have your pony bottle, so if the main tank transmitter dies or fails, you have a whole other tank to save your lifestyle.
The "Stony" bottle:
Yoke is wonderful. A DIN regulator would eliminate the big plastic screw head of the yoke. (One less piece of plastic sticking out. Right now you have the transmitter, tank valve and yoke screw)
Go to a motorcycle shop and ask for some trash inner tubes. Slip a couple of inner tube rubbers on the tank and keep the regulator there.
You don't need the necklace for it. A bolt snap on the regulator will keep it anywhere you want. It is easy to transport all bundled like that. When you are in the water and comfy, you can grab the pony regulator and clip in anywhere.
The elastic keeper also allows you to have any length of hose for the pony regulator and it will not get in the way. Detaching the pony in the water or at the surface is also easier.
Consider getting rid of the metal neck ring on the pony and use a girth hitch with the double ender. It is easier to move the entire rigging to a different pony (AL40 or AL80) and gets rid of a metal-to-metal connection. The other side of the double ender can connect directly to the left chest D-ring.
The bottom rigging of the pony bottle looks like a sheathed stainless hose clamp but you have a metal ring on it. Get rid of the metal ring and put a rope loop under it instead. Girth hitch the bolt snap from picture Q to the pony bottle and the rope length can be as long as you need for the bolt snap to reach your BCD "stony bottom clip".
Practice your frog kick, back kick and helicopter turns in this new configuration. The pony should be horizontal when full and should not interfere with your propulsion or trim.
Please reconsider taking a spare mask in the water with you. Not really necessary for recreational divers but you are diving solo.
If you have a reel, you need a line cutter. The shears should be enough. When was the last time you tried cutting webbing or a line with them using only one hand?
You have a clutch reel, the drum can spin only when the handle is compressed. I have every confidence in your ability to operate this reel correctly. It should not be used with a surface marker because anything but a firm grip means that the surface marker is taking the reel with it and your hand with it. Please consider a finger spool.
Do you have redundant bouyancy?
You can get a surface marker with oral inflation. They provide enough lift to stay in trim and neutral bouyancy.
Some people prefer a surface marker with a pouch. the pouch provides less of a snag hazzard and protects the inflatable from getting nicked or scratched.
Do you have pictures from the back?