Map signatures to replacement text for mobile using Exchange Connector

It would be nice to be able to specify what signature should apply for a given replacement text. The default choice would be the user's default signature, but then you could also choose a different signature. So for example, the user could have a replacement text {A} that triggers the default. But sometimes the user wants a short signature which we've created, so he could change that to {B} before he hit Send. This would also be useful in the case where the user needs a unique signature for mobile.