Hmmm... I do and do not agree with you. The problem is that there is already some people trolling and using the emergency button without there actually being an emergency. This will even be worse when you can use the button twice!
However, indeed, with 2 impostors, the ability to use the emergency button twice can be really helpful!
I have a solution that might solve this:
Add a function when someone uses the emergency button for no clear reason: "Fake emergency". When there is 4 or more players, the users can vote if its a fake emergency, and if over 3/4th of the users say it is, the button cannot be used a second time by that user!
I am not sure if this is possible to implement, but it might solve your issue...
Although this can cause some party trolling!
Idk, maybe people can give some feedback on this :)