I would create a random password as a key for the account and send them the password by bitcointalk. This way management can close distribution.
If they don't take it, its like destroying. And if they realize after a year, that they have a lot of money there, its nice.
Unless the owner of bitcointalk decides to steal all unclaimed coins an year later, and no one will know, as the coins will be unclaimed.
And its rightly theirs, after all, they believed in NEM in the first place and deserve it.
The reasons for not beeing able to claim it now, are manifold, think about it . . .
But, yes, we have to figure out a way, that can not be gamed by others !
(still cannot believe, we´re discussing any other options)