Help me with designing a node

I want to put a node up on my house to act as a repeater or station, but I don't know how to spec it from the PCB available as-is on Aliexpress and other venues.

So - what would you do?

• Which board
• Which antenna
• Which power source (solar + battery?)

It needs to function on an unheated loft in Denmark year-round...

Surely, some of you have done this before, so please halp :)