The meta magic rager is not restricted by the spell levels. A 5th level meta magic rager with the quicken metamagic feat can spend 10 rounds of rage and swift action cast any of their spells.
At least, as written, that's how the ability works. Is does seem kind of weird, but there you go.
When my bloodrager hits 5th level I'm looking forward to using quickened True Strike plus Blade Lash. Add in BAB, raging Strength bonus and a +1 weapon and she will have +42 to trip someone up to 20 feet away. That will eat 11 rounds of rage and 2 spells, but my half orc bloodrager will have 19 rounds of rage by that point. As long as I don't roll a one, anything remotely level appropriate that isn't too big or otherwise immune to trip should fall down at that point. Good times.