[Twisted-Python] Could Service.startService return a Deferred?

[Dustin J. Mitchell]

This is kind of an ongoing bugaboo for me, too.  Buildbot uses
services *heavily*, and at runtime (to support reconfigs, etc.).
We've had to work around issues like stop being called before
asynchronous starts complete using DeferredLocks and other such fun.

I filed a bug with some of my issues -
https://twistedmatrix.com/trac/ticket/6813

It'd be great to fix some of this in the existing implementation, but
#4366 seems to demonstrate that this is impossible without breaking
compatibility.  So, maybe we need to introduce a new service hierarchy
-- perhaps with some ability to use the existing Service classes as
child services.

I'd be interested to hear thoughts on the matter.

Dustin