Kare wa nakanaka no gaikōka da. He is quite a diplomat.
Kyō wa nakanaka atsui. It is very hot today.
nakanaka no kaikyo no mean feat
nakanaka no hayawaza da Sharp work!
なかなか is an adverb/the stem of an adjective, as Mike-san wrote. ほぉ、これはなかなか "Hoo, kore wa nakanaka" can work when seeing beautiful sunglassess since it's obvious for listeners that the speaker wants to say "Hoo, kore wa nakanaka ii mono da. Well, this is quite a good one." As for the rest, no, you can't use nakanaka for those cases.