For sure. Interesting, that is. I did some vegan cooking some years back and tried flax, chia and aquafaba. I seem to think, without remembering well, that the aquafaba worked in a cake, which also had baking powder. Flax meal works fine in GF vegan loaf, but not as well as eggs. ;) Commercial Egg Replacer doesn't work any better, in my very limited experience. I also remember preferring chia, but can't remember the circumstances. All of these are for glue in baking. The only decent ersatz eggs to eat as eggs I've had was scamled tofu with omelette veg mixed in, but nutritionally, it doesn't cut it. Beans have more protein than carrots, but eggwhites are pretty much pure protein. If you want to try it, I'd recommend finding mom blogs that have been going for years, with good comments by people who actually made the recipes. People on special restriction diets become much more tollerant of not-great food, since yum is often the third (or lower) priority. There are some really great vegan cooks out there making really great food, but they're often not the commercially known ones.

Air would be the best substitute.

I might be able to change your mind about deciduous magnolias. Here's magnolia Iolanthe [click image here] Here's magnolia 'Yellow Bird' [click image here] Unlike your Southern magnolia, they will lose their leaves in the winter. But their leaves will also look a little more lush green than the harder darker look on Southern magnolia. One other possibility, if you are sure you are in zone 7 is wintersweet. Kind of boring during most of the year, but during winter it can have nicely fragrant little flowers that can waft its scent some distance in the cold air. But if you think your Southern magnolia was killed by the cold, then wintersweet probably would not do well there. It's a very small tree.

^Yes, Pyrex and other options. Also, depending on the brand of pan, the interior should be 15x10, or close…maybe 14.75” x 9.75”. A 10x15x2 pan isn’t exactly standard, but they do exist and are not the same as a 9x13. ETA - Just thinking…I’ve occasionally halved my lemon bar recipe that calls for a 9x13 pan. I use an 8x8 pan but increase the ingredients by 1/8. You wouldn’t have to as long as you know the baking time would be less since an 8x8 pan is larger than needed for half the recipe.