Closet with sloped ceiling

I'm building a clothes closet in a master bedroom with sloped ceilings. The walls are 3', and the ceiling slopes up at a 45 degree angle. Because of space concerns I need to keep the closet depth to a minimum. But what would that be? The lower I put the closet rod, the farther back it can sit. So what would be considered a minimum appropriate height? And the minimum space to leave in front of the rod? I can figure out what would work for me, but I'd hate to find that my choices will make the house less sellable in the future.
The room also has a walk-in closet, but it's inconveniently located; that means there's alternate storage for long dresses and things. What would a typical buyer consider appropriate?

Most closets are a minimum of 24" deep.

This one’s going to be a lot deeper than 24". With a back wall 3' high and ceiling rising at 45 degrees, if a standard closet rod was hung at 68" high, then I have to come forward 32" just to have the rod flush against the ceiling; probably 34 or 35" to have adequate space for hangers. Add a foot in front of the rod, and we’re talking about a closet depth of 47" plus the width of the front wall. I just don’t have four feet of space available.
I could set the rod at 5', and then maybe just leave 10" of space in front of that. Then the inside closet depth could be as little as 36". That I have room for. But it all entails compromises. Should I fight for every inch of rod height I can get; can I squeeze the space in front of the rod down to 10" or will I regret it; is it better to have a cramped closet or a slightly cramped walking space between closet and bed? I have a queen bed that will actually give me quite a bit of room, but I’m trying to preserve the option of fitting a king in this space. A 40" outside depth for the closet would offer a 26" wide walking aisle next to a king that’s centered on the end wall. A non-centered bed could provide up to 6 more inches of wiggle room.
I just found one website that says you want 63" rod height to hang street dresses. I don’t have any dresses to test that claim. Eking out those extra three inches would be costly in terms of bed space. So this is all about where do I compromise?

Well if you're building the closet (meaning there is no front wall yet), you can build it as deep as you want. I only said that most closets are 24" deep.

As for me, I would wonder if I saw a closet that the clothes bar was much lower than eye level - and I'm not really tall. Now I'm not about to do the math for you.

I lived in a Cape-style house when I was younger. The second floor bedrooms sloped down at both front & back. The closets were on the end walls and were normal height with a normal doors. However they went deep to the side, giving you a normal looking closet with room for lots of storage. If you did that, you might even put in a second clothes bar just high enough for shirts & blouses, at an angle to the main bar.

The interesting thing was that the previous owner had built in bureau space into the short wall....three drawers of clothes tucked out of the way, taking up zero floor space. Of course thee was no table surface provided by that, so you still need some sort of furniture.