Yes, there is a stiffener to keep the lid from bending from the weight of the tower and all. On this lid in particular, that's mandatory.
I epoxied a piece of melamine coated shelving (1" thick by 12" wide) to the lid, and the tower bolts and the threaded drip tray drain pipe run through and are bolted tight over fender washers (all hardware stainless). The bottom layer of rigid XPS foam is also glued down, and a second layer glued over that. The lid is now very stiff indeed - even with the tower, drip tray, sleepers, six filled beer lines, manifold and gas lines all dangling down, there is no perceptible twisting even if lifted at the tip of a front corner. Highly recommended, because a twisted lid would be a major pita, and the stock lid simply had a batt of fiberglass insulation tossed in under the liner and it was very flexible. The R-value of 1.5" of XPS foam is way higher than the same thickness of fiberglass as well, though being at the top of the chest freezer, probably not all that important.
As for all the wiring: I mounted a digital controller in the front of the lid, and it takes 110VAC from the existing dome light feed to operate its internal logic. There's a 12VDC & DC Ground feed through a four pin DIN socket from an external power supply running to a 2.5mm/5.5mm socket on the left side of the lid, which runs a 40mm tower cooler fan, a 120mm general circulation fan on the hump, and an 80mm fan on an Eva-Dry 500 renewable dehumidifier on the floor.
The 12VDC also runs to one side of the relay on the controller, with the other side of the relay exiting the lid and switching an external relay located with the 12VDC power supply, both on a small panel mounted in the back of the dolly.
Then there's the temperature probe wire from the controller, which in this picture terminated at a dangling socket on the right side of the lid, but I replaced that with a 2.1mm/5.5mm socket (different size from the DC power socket) attached to the liner like the one for the DC power (it hadn't arrived before I took that picture). The NTC 10K probe supplied with the controller only had a four foot wire, so something was needed to extend its length anyway, and with this I can replace a damaged probe in seconds (already have two spares wired to matching plugs just in case).
The panel recessed into the back of the dolly has a split duplex receptacle with one side always on (to run the dome lamp and the temperature controller), and the relay-switched outlet (to run the compressor). Power enters the panel via a 15A rated line cord through a mating receptacle. There's a switch to kill AC to the power supply, an LED "DC power good" indicator, the 30A relay that switches the compressor, and a four pin DIN for the DC power and relay control to the lid. The regulated power supply is a cute little thing weighing all of two ounces, so I just stuck it out on a standoff rather than making the panel that much longer.
The reasons for not running the compressor directly from the front controller: I didn't want to have to run two big fat AC lines in and out of the lid, and as the relay on these controllers is the most probable component to fail, wanted to make its life easy by using a low voltage/very low current circuit to drive a beefy external relay, and let the latter do the heavy lifting. The panel takes under a minute to remove or install.
Overkill? Perhaps, but it let my EE side run around and have fun with the design. I call it my "Low Art/High Tech Beer Dispensing Appliance"