The HAB parts as-is are perfect Bigelow style habitats for landed use. There are 2 issues, one of which is aesthetic.

If you add an airlock to the B models, the "down" side of the airlock means that the windows on the landed hab must face at the ground, and zenith, instead of along the horizon line. Small thing, but they'd look cooler with the lights on on the sides, instead of facing the dirt and sky. This just means rotating the adapter 90 degrees.

The second tweak would be to then add an airlock adapter to the C 3/4 parts assuming we end up with a decent way to land them, lol. (I'm looking at YOU, horizontal landers!)

You can see what an EVA looks like under the assumption that a Bigelow is placed with the windows looking out.

Sadly this is far more complex than just 're-orienting the adapter' (because that adapter is also used elsewhere). Because of how the models are done (and composited at run-time), it is actually the model itself that will need to be re-oriented. And because of the animation setup they use.... I'm not even sure that is possible without completely redoing the rigging and animation.

Larger size airlocks -- have been on one of the TODO lists for nearly a year now. I just need more time. Always need more time. Or maybe I just need some unpaid interns. (I think I'm probably about 1 1/2 years backlogged as far as what is already planned; and that isn't counting any new concepts that will inevitably pop up in the interim)

Will investigate re-orienting the parts for a future release. No guarantees on it though. A second (potentially far less disruptive) alternative would be to create a secondary adapter definition (rotating the model in the config), and reference that new definition in the part-configs for the HAB parts -- that way you would end up with two airlock choices, one oriented in each direction. As a bonus, if just adding a second adapter config, it could be done entirely through config files and wouldn't need to worry about mucking about with animations/rigging for the models themselves.

I was thinking in terms of when you move on to habitats, which you had mentioned, not for a current build. I could always add an airlock adapter to a tank, and just use a min height tank (set as structural). It's not a big deal, I had assumed that there was something akin to the attachment nodes, and it might be a cfg issue of rotating the part that way.