If you break the snag and go down that way, Base LV Colm would need to crit the skeleton with a 2% crit (5 STR Colm will 2RKO it) or have a 12 STR Eirika lol, And Artur would need to be super dodgy on the forest tiles. Then Colm would need to stay back to take out the reinforcements while Eirika crosses the snag and bridge en route to the boss.
If Eirika goes east and across the bridge. Artur needs to score at least 1 crit to take the 2 closer Mogalls out of Eirika's way, and then Eirika need to crit the boss for a 1RKO on turn 4 in order for her to be able to get in range of the 2 skeletons by Lute's village.
In both scenarios, Artur and Eirika need to dodge a ton of 40-50% hit rates and Artur needs to kill too many enemies too quickly. If youre comfortable with that much RNG manipulation go for it. I dont care, I will win either way.