I'm really shocked (and yet, from my experience over the years, I shouldn't be) by some of the replies on this thread (and I didn't see some of them that have been clearly deleted). I'm not a doctor, but one potential diagnosis this sounds like is this one: https://pubmed.ncbi.nlm.nih.gov/28537947/
I'm a notoriously picky eater; not to the extent of having sought a formal diagnosis or that OP's husband sounds like he is, but still particular. There's one event that DW and I have an obligation to attend each year, and while there are large quantities of food (there's roughly 30-40 people in attendance), I won't eat any of it. DW has expressed concerns on multiple occasions in fact that I would rather not eat for the 16 hour entirety of the event (and sometimes we wake up late enough, that we do not even grab breakfast before the start of it), and encouraged me to find "the least objectionable food" there (I swear it sounds like Sheldon's "least objectionable activity" friendship board from The Big Bang Theory every time DW says it), and my gag reflex kicked in as I started to try to eat it.
With regard to OP's question, I don't have experience with the mobile ordering, so I can't speak to that side of it, but I've had very positive CM interactions with reasonable substitutions. I've not had breakfast there, but I have had lunch there, and while your mileage may vary with the particular CM, I've been successful at getting most ingredients I haven't wanted removed, so long as they're not pre-mixed, which shouldn't be the case with this particular sandwich. Also, a lot of times I've been successful with cheese substitutions (in case it's not an objection to cheese in general, but just brie in particular, which I also don't tolerate well). If meats are more his thing, I don't know if you have had successes with charcuterie boards in the past, but theirs looks delightful, and just wanted to offer it in case you missed it.
Good luck on your journey. The Be Our Guest restaurant has become a memorable part of every trip for us.
I'm a notoriously picky eater; not to the extent of having sought a formal diagnosis or that OP's husband sounds like he is, but still particular. There's one event that DW and I have an obligation to attend each year, and while there are large quantities of food (there's roughly 30-40 people in attendance), I won't eat any of it. DW has expressed concerns on multiple occasions in fact that I would rather not eat for the 16 hour entirety of the event (and sometimes we wake up late enough, that we do not even grab breakfast before the start of it), and encouraged me to find "the least objectionable food" there (I swear it sounds like Sheldon's "least objectionable activity" friendship board from The Big Bang Theory every time DW says it), and my gag reflex kicked in as I started to try to eat it.
With regard to OP's question, I don't have experience with the mobile ordering, so I can't speak to that side of it, but I've had very positive CM interactions with reasonable substitutions. I've not had breakfast there, but I have had lunch there, and while your mileage may vary with the particular CM, I've been successful at getting most ingredients I haven't wanted removed, so long as they're not pre-mixed, which shouldn't be the case with this particular sandwich. Also, a lot of times I've been successful with cheese substitutions (in case it's not an objection to cheese in general, but just brie in particular, which I also don't tolerate well). If meats are more his thing, I don't know if you have had successes with charcuterie boards in the past, but theirs looks delightful, and just wanted to offer it in case you missed it.
Good luck on your journey. The Be Our Guest restaurant has become a memorable part of every trip for us.
check out one of the many maps for the restaurants and find something for Plan B if nibbling at the tray is not going to fill him up.