Multiple Alias This

[dsimcha]

Is the limitation that one may only have one alias this per class/struct a
temporary limitation that will be removed once higher-priority stuff is
finished and some ambiguities are resolved, or are things likely to stay this
way?  On the one hand, allowing multiple alias this would cause ambiguities
similar to multiple inheritance.  On the other hand, only being able to define
one implicit cast per class/struct is pretty limiting and allowing only one
alias this seems like a huge cop-out.