I note that #class was removed from specialSelectors (nilled entry) so as to not use the VM hack which fetches the class without sending a message.
Pharo prefers the regular message send.

But next to that entry, there is #blockCopy: which was formerly used for blue book BlockContext.
BlockContext was removed from Pharo...

So that makes two available slots for optimizing most used (sent) messages...

We might choose some candidates and test on some macro benchmark if ever that really makes a difference.