I know that this combination is strange but I want to try it because of current characters pull in Simulated Siege. And my opinion, it is strange that it doesn't work.
Relying on description of Ismael skills and visual information it feels like it should work.
At least in description you have a condition - "only one elemental Tank/Breaker". And this condition is met because in team selection UI the game showing that Ismael will be Amplifier. But in battle amplifier buff doesn't apply after switching characters (same with buffs after QTE).
#Ismael Amplifier perk doesn't work with Elemental and Physical Tank in one team. (Maybe UI issue)
delicate wolf
So it's a question if it is intended behaviour. Because if yes - there is questions to UI. If no - there is question to in game interaction.
Just for example. What shows UI for expected behavior with 2 elemental tanks or elemental tank and amplifier.