Given proper design and installation, all contact-type oil seals will work fine for a long time in a shaft-down installation ... until they fail.
Weirs, drywells, etc, are the logical evolutionary response to a perceived or real need to avoid contamination of whatever is being mixed even when the oil seals leak.
Need a super-short box?
Can afford regular preventive maintenance?
Are really tall when you're sitting on your wallet?
Given that last, nearly anything is possible.
Mike Halloran
Pembroke Pines, FL, USA