Is Joost still active in the FPC community? If so, I'd be interested to hear his opinion on all this...
AFAIK not much. The attributes feature is rather complete and working. I was asking few times about state of attributes in the past. Free Pascal is a "fun driven" hobby project where core members who do the actual work can add what they like, there is no common vision (probably Delphi 7 compatibility is the strongest point). FPC core is reluctant to spend their time for things which are no fun or not needed by themselves or doesn't fit in their world view. Worth to note that FPC core doesn't like the syntax for attributes.
I was FPC core developer but I have permanent ban (from Michael ofc.) so I have no influence. The only what I can do to help is to add attributes to NewPascal. Probably this movement can be motivation for FPC core. For example worth to note that was really hard to put my Generics.Colellctions into FPC trunk (I was fighting for this for very long time - the resistance was really strong without any rational reason), it was added to trunk only when I decide to release Generics.Collections together with NewPascal (the same happened with RTTI module).