Well, this isn't really a matter of remapping, but of changing the behaviour in the application. If you just remap tab to do this, you lose the ability to insert normal tabs, as clearly keymaps don't contain info such as "do this if block is selected, this otherwise". So the shorter answer: No, unfortunately it can't really be done :-(.

What's worse, you lose all tab triggers, so half of the commands/snippets in the bundles can't be executed anymore.

-- Sune.

Haris