Personally, in all my 25+ years of programming experience I've never seen the use of hex floats.
I can understand their usefulness when a precise number is wanted, but I don't consider this a priority for AngelScript. Personally I will not spend time on implementing this anytime soon. However, should you feel inclined to implement it yourself I'll gladly include it in the library.
Paphi's other suggestion of custom literal constants, i.e. tokens that get converted to a registered type during the build itself (similar to string constants) is also a low priority item, and still on my to-do list for a distant release.
The fact that the 'p-24' part was ignored in your script above must be a bug. It should have given you a parser error as the 'p' should have been interpreted as an identifier. I'll look into this and have it fixed.