I still develop mainly in Delphi. Object Pascal is definitiely awesome. Im programming in Delphi since 1995, so just 20 years now.
Wow, time has passed 
Actually I did something like this for one of my own projects. i thought about adding a scripting language and then went to adding Delphi itself.
I used the freePascal compiler to have the “scripts” compiled either in advance, or dynamically before each execution. This also allowed for self modifying code with all its possibilities.
One step further:
If a blueprint node just contains some logic that generates a data output based on data inputs; and there is an option to have them available as self contained, compiled, code fragments (DLLs), then basically any language could be used to create blueprint nodes.
All it would need is to define the calling convention for the exported functions and parameters of the DLLs.
If there is then a field in the details panel that lets me specify the command line compiler call, then anyting that can compile into a DLL is good for UE4 coding…
…Just my two cents on this
Cheers,
Klaus