.thumb.png.3d8ac6f0f3309aec01e9eac0c8dc3b36.png)
I'm sure he can rush in with no problems.
I think you should play it like you think Finn would naturally react in this situation.
Mechanically, you can run in, they can run out. PCs can move through each other's hexes with just 1 extra movement point. It COULD slow things down in the doorway, but that would realistically happen. I like the chaotic flow of combat as it could/should/would happen on a second to second timeframe, not how it's planned out strategically by the whole group second by second.
Just go for it!