The Athlete Guide for 70.3 NZ makes no mention of the rumored ban of bottles and bladders down the kit for 2024.

I believe IM follows the uci rules for this type of stuff so if they don’t ban it then IM won’t ban it. That’s what I was told my Andrew messick last year.

It has been banned by the UCI for many years.
https://www.cyclingnews.com/...e-over-camelbak-use/

Think you need to do better than that, Ben. Which cyclists have been DQ'd for breaking whatever rule (some random or Italian mag thinks) might apply.
What is the current UCI Rule?
2011: Schleck has "nothing to hide" over Camelbak use - Leopard Trek rider didn't know he could possibly be breaking UCI rules.
ICU judged he had not broken the rules (UCI rule 1.3.033: "it is forbidden to wear non-essential items of clothing or items designed to influence the performances of a rider such as reducing air resistance or modifying the body of the rider."
Possibly because he wasn't "wearing" a bladder, he was using it to drink from (and it could be drunk from).
What is Sanders meant to do when between trash zones in Oceanside and finds the bottle he's picked up won't fit in his cage? Do a Charles Barclay and accidentally drop it? Or responsibly put it down his top till he can ditch it 'legally'.

It has been banned by the UCI for many years.
https://www.cyclingnews.com/...e-over-camelbak-use/

Think you need to do better than that, Ben. Which cyclists have been DQ'd for breaking whatever rule (some random or Italian mag thinks) might apply.
What is the current UCI Rule?
2011: Schleck has "nothing to hide" over Camelbak use - Leopard Trek rider didn't know he could possibly be breaking UCI rules.
ICU judged he had not broken the rules (UCI rule 1.3.033: "it is forbidden to wear non-essential items of clothing or items designed to influence the performances of a rider such as reducing air resistance or modifying the body of the rider."
Possibly because he wasn't "wearing" a bladder, he was using it to drink from (and it could be drunk from).
What is Sanders meant to do when between trash zones in Oceanside and finds the bottle he's picked up won't fit in his cage? Do a Charles Barclay and accidentally drop it? Or responsibly put it down his top till he can ditch it 'legally'.

Not IM but bottles (or owt else) placed in that way are not allowed in T100 races, according to the T100 appx in World Tri Rules 2024 (published last week):
World Triathlon Competition Rules (13 February 2024)
https://www.triathlon.org/...es_2024_20240219.pdf
APPENDIX V: T100 TRIATHLON WORLD SERIES
10.3. Specifically, the following items are not all[owed]:
a.) Bottles/hydration or any other insert located in the front of an athlete’s race suit.
b.) Any insert in an athlete’s calf sleeves.

To be clear, I think this 'stuff down the front' is ugly and should be banned, with monitoring and control exercised in and at the exit of T1. A bladder on max volume 500ml down the front is acceptable imho (and too small to have aero benefit). Subsequent bottle down the front to avoid littering should result in penalty if extended over time (eg beyond a 'trash zone'). I have suggested a first draft rule amdt in one of the long 'bottle down the front threads on here.
Here's some UCI explanatory notes (Jan 2023): https://uploads-ssl.webflow.com/...-_20230126_-_ENG.pdf
UCI Regs - ARTICLE 1.3.024 BIS
CAMELBACK
Hydration is an essential physiological consideration for athletes during a physical effort.
Neither bottles nor camelback systems should diverge from their original function.
There is a significant risk of camelback systems or any similar devices being used for other
purposes than their original function. For this reason certain restrictions apply if they are to
be used in competition:
• The camelback system is authorized for competition solely for the purpose of rehydrating
the rider.
• It must not be the case that the system, presented as a way of improving a rider's
hydration during an effort, is accompanied by an "aerodynamic clothing" advantage, in
this way deflecting the camelback system from its original function.
• The liquid container must not be capable of holding more than 0.5 liters and must not be
a rigid shape liable to be considered as a device for improving the rider’s aerodynamic
qualities.
• The use of the camelback system must not modify the rider's morphology and must thus
be directly attached against the body. [ie no low-hanging gut arrangements]
• The use of the camelback system is only allowed on the back of the rider.

Magnus has a bottle down his kit at Miami. Apparently the rule is you can grab one from an aid station and but it down your kit as long as you use it and discard it. Magnus hasn’t touched it once the whole race.

If any of these things were remotely practical or made a difference, maybe it would be relevant. Rules don't need to me more specific if no one will bend them that way.

The bigger issue is the time between using the bottle, replacing it, etc.

I just think banning this is stupid. I used a 1.5 liter bladder last year and it worked great. I reduced the number of bottles in my frame and avoided having to use aid stations. The bite valve just sticks out the top of my Tri kit and it’s super easy to drink off. I know it looks ridiculous but it’s convenient.

Plenty of wiggle room there.

How many aid station bottles can I have down my kit?

Does it have to be aligned with my torso? What if it's faster to put in sideways

Can I fold it in half to increase it's area?

Can I put one bottle on the inside of each sleeve and another down the front?

If they're also handing out gels can I grab 20 of those and keep filling the space?

Plenty of wiggle room there.

How many aid station bottles can I have down my kit? ONE
Does it have to be aligned with my torso? What if it's faster to put in sideways? SUIT YOURSELF
Can I fold it in half to increase it's area? HOW DO YOU FOLD A BOTTLE
Can I put one bottle on the inside of each sleeve and another down the front? NO
If they're also handing out gels can I grab 20 of those and keep filling the space? YES

But the TRI Rules (2024) say 0.5 litre bladder only, on the back not the front.
We need to have a regime where an athlete can put their gels and ONE bottle picked up on course down their front (see Sanders or LCB at Oceanside 22). We can stop anything (other than a bladder of pint volume) being put down the front in T1 (by a ref stopping athletes at the dismount line with a threat of 'sort it or DQ').

These rules are fine, no issues. But they're clearer than the current rules. That's my issue. At a certain point it's going to need to be anything goes or nothing goes.

And the aid station bottles are usually those disposable pop top ones, easily foldable/bendable. There is definitely an optimal way to put that generic bottle into your kit.

Wholeheartedly agree. If I know anything about the world though, the fact that there is no money to be made means there will be few insiders defending it, and it will likely be banned. Fancy aerobars, ceramicspeed, Giro Aerohead 2, all of these have less effect but a high price (and corresponding high profits). Ain't nobody making money off $15 bladders.

If we're going to start legislating triathlon based on 'how silly things look' then we're going to have a laundry list of prohibitions.