Write a C++ source highighter that uses Clang to identify the various syntactic and semantic elements.
Write a web template/blog engine in C++.
Turn Clang into a two-pass compiler so that forward declarations aren’t needed any more. Do templates make this impossible? Find out.
Find a way to get rid of most/all of the undefined and unspecified behavior in the C++ standard.
Find all the usable C and C++ source in the world, catalog it, and make it available for use.
Solve text encoding.