Outdoor deployments, which are standalone in nature like this can be challenging and complex due to the amount of moving parts and factors involved. Based on your initial questions here are my thoughts:
In terms of co-locating equipment you should be good to put everything into a single box, just make sure your solution is adequate (as you have inquired about) to deal with the environmental conditions.
A consideration is not just the MFR of the enclosure but the IP/NEMA rating being adequate. Also you should make sure a robust material is used for long term reliability of the box itself, I would only recommend Fiberglass or Metal
Heat will be your biggest challenge and no matter the solution. It will affect you in a couple of different ways that you'll want to factor into your design:
- Solar loading I have experienced, and would recommend you expect anywhere between a +15F to +40F delta increase in the internal box temperature no matter what you do. This range will vary based on the cooling design, temperature, spurious internal heat emission, material and color of enclosure.
- Lowering overall lifespan of internal components. This means you should watch out for long term warranty obligations and etc - considering there isn't a whole lot you can do to avoid this. (Unless you overkill it with a very expensive/heavy/power hungry actively cooled solution)
- Derating your power system. Any time you get high PoE budgets you'll need a sizable power budget. This gets especially compounded in hot conditions where power supplies can derate up to 50% of the stated load capacity in temperatures that get to the levels you talk about. So most importantly I'd plan on doubling the power transformer unit based on what you calculate requirements to be.
Also - I've always designed some type of self healing feature or remote reset/monitoring capability into systems like this. Whether that be a ping watchdog function on the switching/wireless equipment, configuration of the camera or a standalone relay device - it's much, much cheaper than a truck roll for maintenance.
Good Luck
Chris