I work for a construction company and we were looking for a mobile camera solution.
This is what I came up with and it works great. We can move it around easily and in most areas the Mobile Broadband gets adequate reception to operate well.

Step 1: Get the Parts

Here are the parts I used for this enclosure assembly.

-AXIS 215 PTZ-E Network Camera

-Linksys Wireless-G Router WRT54G3GV2-ST

-Sprint Mobile Broadband Card PX-500

-Orbit Outdoor Timer Cabinet

-Strain Relief Cord Connectors 1/2" and 3/4"

-Heat Shrink Tubes

-14AWG Replacement Cord

-1/4 Bolts, Lock Nuts, and Washers

-Louver Vents

-50mm Fan

Step 2: Build a 50mm USB Powered Fan

Here is a link to an instrucatable about building a usb fan.
https://www.instructables.com/id/USB-Desktop-Fan/

This is how I did it.
A 50mm usb fan will fit over these louver vents.
Make sure to use a usb plug with a 1" long protrusion from the device. Anything longer that that wont fit between the router and the cabinet. I found a retractable usb extension cord made by ZIP LINQ that works great.

Cut the plug from the fan and the female end from the usb plug. Make sure to cut the other two data wires at different lengths so they don't touch. It will cause problems if they touch. Also cut the foil and shielding wires back.

Before soldering the wires together slip one 3/16" full tube over all the wires and two 3/32" pieces of shrink tube over the small wires . Make sure to pull the tube back far enough so they don't start to shrink while soldering. Solder the red with the red and the black with the black. After soldering shrink the small tubes over the small wires soldered areas using a heat gun or even a lighter. Be careful not to burn or melt the wire sheathing and be sure to cover all the exposed wires. Then shrink the larger tube over all of them. This will make the wiring safer and better looking.

Step 3: Assembling the Cabinet Components

Start by disassembling the cabinet.
Take the door off the GFCI out and the mounting plate out.

Drill 3 2" holes into the cabinet.
Drill holes for the 1/4" mounting bolts.
This camera came with a template for laying out the mounting holes.
I put one louver in the front door and one on the back of the cabinet.

Install the Strain Relief Cord Connectors.
Wire the 14AWG cord to the GFCI plug.

Install the louver vents.
Put a bead of silicon around the louver for water proofing.
Make sure the vents are faced the correct direction.

To mount the USB fan use spacers and predrill holes for screws.
Make sure to use screws that are long enough to reach from the back of the fan into the cabinet. Find spacers that will fill the space between the fan and cabinet so the fan sits above the louver.
Don't let the blades of the fan touch the louver.

I used 1/2" spacers with 1" machine screws to mount the fan in place.

Mount the camera.
Put water proofing foam tape around the edge of the camera mount before attaching the camera to the cabinet. Or use silicon after mounting the camera to water proof around the camera mount.

Step 4: Setting Up the System.

Mount the router and start plugging things in.
I used double back tape to mount the router in place.
Stick the mobile device into the router, plug the Ethernet cord from the camera into the router, plug the usb fan into the router, and plug the power cable into the router. Plug the camera and the router into the GFCI, then plug the main power cord into a power source. After several seconds your system should be running.

Plug a computer into the router via Ethernet.
There are a few settings you might want to change within the router and camera.

Its a good idea to purchase a static IP with your mobile device. Set up the camera and the router with the proper IP settings.

Set up wifi so you can access the router when its in hard to reach places.

This router is set by default to Connect on Demand: Max Idle time 60 Min. Which means that it will disconnect the internet connection after 60 minutes if its not being used. And it wont reconnect unless someone or something tries to connect to the internet through the router.
Change the setting to Keep Alive: Radial Period 180 Sec. This will keep the system connected at all times and if for some reason the connection is dropped the router will try and reconnect after 180 seconds.

Change some of the camera settings to help speed things up.
Changing the image compression and frame rate can greatly improve response time when using a mobile internet card.

So here it is a Mostly Remote Camera. It has remote internet but not remote power yet. A solar solution would be nice.

The extra 3/4" hole can be used for antennas or a land line connection.

Step 5: Mounting the System.

Its up to you to figure out how you want to mount your system.
I built this stand so I could put it on a roof top and move it around easily.

And it looks like this.