None of these wood species are inherently weather resistant. They all depend on the paint, stain or sealer finish for weather protection. So the answer to your question is found in how you propose to finish the door. Maple is a light and very hard wood, It will take stain, sealer or paint equally well. Douglas Fir is considered a soft wood, but one with great structural ratings, when used in framing lumber. It is a light wood, but not one that is particularly attractive when stained, IMO. Mahogany is a dark wood, and probably the most naturally weather resistant of the three. It becomes even darker when stained or finished with a clear sealant. Painting Mahogany makes little sense. Hope this helps. Good luck with your project. So much depends on whether you will paint or stain the door, or you think you will leave it weather naturally. The latter is probably a mistake.

I don't know about your climate but my parents have a cape cod style house with no front porch and a wood door with sidelights and it is going strong after many years. If you want a saltbox style house, a porch wouldn't fit very well I wouldn't think. I was also thinking you could recess the door a bit and panel the sides of the recess (you see this a lot with Georgians) but I was thinking you wanted a georgian style house not a Saltbox style one . . . Are you doing brick or siding? If you are doing brick, you could recess the door a bit into your anteroom (this could leave an area for closets on either side which you could make attractive - I'll try to find a picture), but you would lose some of the focus of the spiderweb look. I think this other look is equally attractive and can be really beautiful but it may not be what you are looking for. It would protect the door more though!

Re: painting, just remember this is not a room it is your exterior. Whatever color you paint it should go on your other exterior (non brick not trim) surfaces unless you close it in and screen/wall it. Just for fun, I really love this where steps go all the way around instead of railings. My deck is like this, I love it. It would look great in brick like this, with the brick pillar as well. Also like these, although any work like this seems like a great opportunity to face the stairs to the street as has been mentioned : ^^ no double columns for you (too fancy) but I love the brick walls and stair railings ^^Forget the style of the beams but the brick pillars at base of stair with white/cream railing returning to simple white posts would be nice What not to do: bulky pillars are all wrong for the house^^ ^^awesome with simple railing

A sliding door vs. a sliding window? Both should give about the same functionality for egress and an alternative entry point during the renovation. The rub on the sliding doors is that they will be more expensive (especially at a custom sized opening) and will usually have more heft on the frame and door sash (i.e. less glass) than a sliding window.