possible, yes ... a wise plan, not so much

that said, based on schedules, the outbound is a redeye and the return is the first flight of the morning, so there are a lot of options for recovery back to SEA; in fact; I'd guess the inbound 738 turns back to LAX (leaving half an hour later, with a connection to SEA) -- only $20 and a couple extra hours for ~1200 additional miles

but again, checking a bag on a MR