Even though it doesn't make sense to do this, can't a plan allow in-service distributions prior to age 59 1/2?

Not of pre-tax deferrals (without "hardship") or QNECs, but in-service distributions of company contributions, after-tax contributions and rollover contributions might be allowable (subject to certain other restrictions on holding periods, vesting and such). Unless it's a safe harbor plan, or possibly a few other Code provisions, which explicitly restrict distribution.