What are the major kashrus/halachic issues with going to a non-kosher restaurant and ordering, say, [kosher fish] and vegetables; dressed with only extra-virgin olive oil, salt and pepper; double-wrapped in tinfoil and baked, served on paper plates with disposable cutlery--a dish which would seem reliably kosher under many circumstances?
I can think of the following potential problems. I am wondering if each of them in fact applies to the situation, or if there is room for leniency within any of them. I am also wondering if there are any I have missed:
Maarit ayin/chashad: Giving the appearance of doing something improper by ordering at a non-kosher restaurant.
Lifnei iver: Potentially misleading Jews that the restaurant is kosher and thus causing them to sin by eating there.
Bishul akum: Potentially eating food that is treyf insofar as no Jew was involved in the cooking.
Questional ne'emanut of non-Jews - There is an idea that we don't say ed echad for non-Jews; that is, that we cannot trust the supervision of those who are not themselves observant (or at least obliged) in kashrus and/or Shabbos. We can't watch the kitchen and thus cannot know that the waiters/chefs are actually doing what we said...and there is no halachic basis on which to trust their word.
Questionable kosher status of the knive(s) used to cut the salmon and vegetables. This would be of particular issue if the salmon were cut while hot, and/or if any of the vegetables were davar charif ("sharp"). (If the food were not sharp, but only hot, I could see this as possibly falling under a leniency for stam keilim einan b'nei yoman.)
Possibility of (very small) bugs in the vegetables, since even nice restaurants do not necessarily check to halachic standards.
...Can anyone comment on these, or add?
(Motivated by this advice on eating kosher on a cruise line--in particular: "I was advised by my Orthodox rabbi that it is permissible to have the chef cook double-wrapped fish and vegetables in the oven as long as the knives are clean and nothing is added to food.")