At the moment, the logic which defines when an app is scaled up or down is hard coded. Flexibility is needed to specify the metric (e.g. concurrent connections, CPU load, application-defined) and thresholds.
bug 1057183 enables this beginning in OSE 2.0.3 - you can substitute anything you like for the haproxy rules. I don't know if that actually enables you to do the specific things you mentioned, as you have to get the metrics from somewhere, but you can certainly supply your own logic. This is extremely unlikely to be backported to OSE 1.2. Shall we consider this RFE completed once 2.0.3 ships?
No need whatsoever to backport to 1.2 - that would be a complete waste of effort. Yeah, I think there's enough in 2.0.3 to close this RFE for now - please go ahead and do that.
Sounds good.