nowadays, it's not much of an issue now... unless you do 1-5 which had oscar in it. But by then, you should have at least one ship (usually a CL) who can do OASW at that point (which happens to be Isuzu K2). Since difficulty selection has been introduced, it's not really scary anymore if you happen to inflate your HQ levels. However... if it was Pre-Winter 2015 event, you are truly screwed.
Anyways, just remember to level your CAs and CVLs too since you can pretty much level your BBs and CVs on it's own.