Thanks to the great advice in this thread I designed a reference board. Since I live in the tropics I wanted something to have fairly good moisture and humidity resistance. I used Conrad Hofman's MML ltc1027 reference as a basis with some additional protection and the temp sensor, also the LTC1027 noise reduction mylar cap. Decided to skip the NTC temp compensation for now, until I can characterise it and see how it goes.
All critical components are hardened against humidity, ltc1027 LS8 package for instance, capacitors and resistors are moisture resistant. The only thing that isn't is the trimpot, well and non critical power regulation components. I kept the costs fairly low as well. Most expensive being a few wirewound resistors and the reference itself. Haven't done the math on it yet but I think in total around $50 worth of components (I usually order in multiples).
The weird J connectors on the edges are for the copper bridges for easy hookup and measurement with grabber clips. That weird orange cap it's just an aluminum electrolytic.. couldn't find the right footprint for some reason, but the holes match. Done in KiCad.
Anyways thanks to: Conrad Hoffman, pitagoras, lars, Kleinstein, David Hess, Andreas and others I forget to mention in this thread!