Walter is right about transitive readonly - here's the alternative

[Johannes]

$.02: I'm a D noob (but I have followed the project in lurk mode for a long time) so I should probably keep my keyboard shut, but -
can't you call it something else than "shared"? It seems to me that with a variable that gives you a compile error if you're trying to reach it without using special commands, the intuitive name isn't "shared". I won't offer a suggestion for another name though since I'm not well versed in thread programming.

Otherwise, what you're saying makes good sense to me.