I think I've tried every possible solution to this and before I resort to SuiteScript for this I wanted to make sure I'm not missing something.

Requirements:
[LIST=1]
[*]Send email to Transaction Sales Rep when a Custom Record ("foo") has a specific field modified.  Foo is joined to Transaction.[/LIST]
Problem(s):
[LIST=1]
[*]A "foo" search will let me setup criteria in the Email > Updated Fields tab to catch the modified field and although I have a join to the Transaction I can't access the Sales Rep's email in the Email > Recipient From Results tab.
[*]A Transaction search will NOT let me catch the joined field's changes (there are no joined fields available) but WILL give me access to the Sales Rep's email.[/LIST]At this point I think that I'm out of options.  I created this thread with the hope that someone may have a trick to workaround these limitations.