Subclass - protect from change?

I'm just wondering if there's a certain level when a subclass is protected from change or can it be changed at any level? Many have subs that are more valuable than the main class. For example, main: dorf, subclass1: sagitarius, subclass2: necro.

Now wouldn't it be a pain to get hacked and find you have a level 40 elpy instead of a sagitarius? Worst if both subclasses can get changed. Losing gear is bad enough but losing all that work with just a few clicks is downright painful.

Now that's an idea >:)

j/k . But there are no restrictions on subclass deletion.

Hm good idea though, you could destroy months of work in a few clicks way faster than delevelling or deleting