Also is this your first build?

I understand the wisdom in getting materials now for a far off project since you expect the prices to rise in the next 10 years. I just wanted to add some food for thought. Before I made my first guitar, I had a very specific idea of what I wanted my "dream guitar" to be once I built up the chops to pull it off. The more exposure I get to hand/custom made instruments the more my tastes evolve. If I sat down to lay out my "dream guitar" today, it would be nothing like what I thought I wanted. Maybe it would be more accurate to say that I no longer have an ideal guitar in my head; there are just too many flavors to enjoy. But I don't see myself ever making the guitar I thought I wanted back then.

I am working on my first acoustic right now, but I will be building this in the future, I expect 8 to 10+ years. I simply wanted to collect the materials now because high value tonewoods and materials are getting rarer and rarer.

Thrice

By the way on the topic of the back and sides, the person I am buying it from says it is flatsawn, however, it is old, stable, wonderfully figured, and has an insane tap tone. Should it being flat sawn concern me at all in terms of stability and tone? I do have a flatsawn bois de rose live edge slab (too thin and narrow for a guitar, it is going to be made into fingerboards and headplate veneers) that is also really stable, wonderfully colored, and has hands down the best tap tone of my entire wood collection, surpassing even my pieces of brazilian and african blackwood, so I am genuinely wondering if it doesn't matter in this species.

Every wood is more unstable flat sawn. I don't know if anyone has data on that particular species or not though. Even suppliers now are selling completely Flatsawn Woods and marketing them as (highly figured lol) and many beautiful guitars are being made from them. Who knows what those woods will do years down the road from now, however I wouldn't be concerned if the instrument was taken care of. Meaning kept in a humidity controlled environment.

Tone wise, no difference.

I know its done but for me thumbs down flat sawn guitar sets --- especially if there is any curl. Simply not worth the possible build and future humidity problems --- been there done it $.02

I have some highly figured mahogany that is flat sawn and I plan on using it for guitars. But that's mahogany which is known to be very stable. Anything else I'd probably take a pass on as well.

Could care less about the ivory, if you got it, the animal is dead. But, (knowing ivoroid does not expand like wood over time), one would expect Mammoth ivory to be rather brittle, comparatively. Might be something to consider if you expect the instrument to outlive you.
Concerning taste change over time. My first guitar (the second time around) was an 0-45 BRW. What I like the most is my ladder braced grade B red spruce and figured white oak Parlor.

Good luck on your quest...

ivory is only brittle if you try to bend it like plastic binding . There are many ways to bend ivories, one method used in the 19th century and before says that it needs to be soaked in hot water and either phosphoric acid or, if I remember correctly, sodium carbonate (don't quote me on that). It then needs to be re hardened with something called "dry decrepitated salt". This is possibly how martin bent the ivory binding their guitars back in the 19th century. That being said, frank ford says he has bent it on a bending pipe as well. Ivory is very strong, and when cut correctly in relation to the growth rings on the tusk, is usually quite stable.

I'm building a little size one out of some wood that looks like yours. It wasn't quite wide enough so I added a center strip and will use a little heavier binding/purfling scheme to "grow" the back.