Support for more granular triggering stream selection for joins (expand 'unidirectional')

I often need to join multiple data windows in Esper like this:

insert into targetWin select ... from
winA inner join winB on ... inner join winC on ...

In many cases, I would only want to trigger the insert when events arrive in winA or winB, but not in winC. In that case, I would build two separate EPLs:

insert into targetWin select ... from
winA unidirectional inner join winB on ... inner join winC on ...

insert into targetWin select ... from
winA inner join winB unidirectional on ... inner join winC on ...

I would be nice to have a similar keyword which lets you specify more than one event streams which trigger the EPL, for example like this:

insert into targetWin select ... from
winA directional inner join winB directional on ... inner join winC on ...

Alternatively (or in addition , there may be a keyword to specifically exclude an event stream from triggering the EPL like this:

insert into targetWin select ... from
winA inner join winB on ... inner join winC nondirectional on ...

Note that in all cases, it would still be desirable to get the latest value for the join from winC (the way unidirectional currently works).