Manganin solders like Cu... It does need some lead length to be effective so the easiest way would be to wire the socket point to point. It's all about the numbers of wires and cross section, so a carrier for the socket wired with the minimum numbers and sizes of wire are best thermally.
On by NIR photometer I got an extra degree C for every copper wire I swapped with manganin (~ #30). Since then I've picked up some very thin wire but haven't tried it yet. The NIR cold finger is at about 208k (-65 C) in a 22 degree ambient with water cooling. The thin stuff (0.04mm) is off the normal wire charts, and I would only use it if both sides were mounted.
For these temps you really need a vacuum "cryostat" and 4-5 stages of TEC cooling or dry-ice. I would not suggest it for the general thread of this project. IMHO, If you try to turn this into a really state of the art camera, it will loose it's more general appeal due to expense and build difficulties. Comments below are only comments... ;-)
If you slot the PCB, add vias on each side of the slot so the traces can be cut and wire jumpers put in. That's pretty easy and non-evasive. Then someone can make the change if looking for that extra degree or three of cooling. If the vias are spaced for a header, the personality board is a slam dunk for those that want. On the ground, you want a "single point ground... usually at the analog input of the A2D. If you put a ground plane under the socket that is isolated from the main (analog) ground plane, connect it with a trace as close to the A2D as possible.
Also note, I am a hacker at this stuff!!! There are likely others on this thread and Hippie is probably one of them, that are way ahead of me.
I made a TEC controller that works pretty well. Had I used SMT parts I could have made it two channel and wish I had. What I did do was to add a "proto" area, a bunch of vias with access to the extra unused op-amp, pwr, gnd etc. Nice to build in some flexibility. A via on a signal you may want access too can really help later. 2 channels?-- one for the cold finger and one for a thermal shield around the cold finger sensor... for my NIR photometer.
If you have a proto board and want to, I have access to a Spectrum analyzer and near field probes. Would be easy to do a quick scan of the board and check for radiated EMI and frequencies. No CCD is needed but it would need to be powered. last half of the video- https://www.youtube....h?v=CQgJmmn-eSE
Disclosure- I sell Rigol products in the Pacific NW, but that's why I have access... :-)