Check Odin architect mod, high quality buiding mod, looks vanilla.

Additional ladder would be great. I really don't like the 45 degree ones due to how silly characters look when walking up them.

Trapdoors would be awesome, too. They'd be very similar to shutters so I don't see why they couldn't be added at some point.

There's been no talk of that, they'd certainly be welcome. Wooden trap doors would probably be a better fit than modern manhole covers though, those are from 1860 AD.