I think there are two issues here. One is starting services on demand. When the web subsystem starts, can't some constituent services can be made Mode.ON_DEMAND, and others (i.e. the deployers Mode.IMMEDIATE). And then war deployers add a dependency on the ON_DEMAND services.
Making some services ON_DEMAND would need to be controllable though; there is a PRD requirement to allow turning that off. That could be configurable at the subsystem level, although I think users would prefer a more global configuration option (maybe on the profile element???).
The other aspect is getting connectors to start at the end of the overall startup, a la what the JBW connectors do in AS 4/5/6. That seems like it will involve having connectors depend on some service that encapsulates the overall startup.