That's the challenge and the purpose of it. It even warns you that it's extremely dangerous to solo for good reason. That's the one single skill that puts Hilla apart from other bosses so it should be kept (unless you want it to be another mindless boss that just stands there doing nothing).
there should at least be a way for you to escape without breaking out (Houdini.)
That's her design, for her not to be solo'd in the first place. It was designed for party play and that's what happens when you don't have the right resources. This is no different to the 1 hit ko's Arkarium does, and heal received by his minions (cannot kill without a mage). By asking to remove the cage or escape is equivalent to asking Nexon to make CWKPQ soloable.
It's just the design itself, and there's not much to argue about it.