At the moment, a global block is, by default, not active on Meta-Wiki because the user may need to appeal. However, this is being exploited by some cross-wiki vandals, who are moving their abuse to Meta.
For known cases, it would be helpful for stewards to enable the global block on Meta from the form itself, in the form of a tickbox.
This box would, by default, remain unchecked. But in the case of abuse, we could use this box to enable the global block on Meta-Wiki.