To the point about SRX240H2 availability. As of 1st May the SRX100, 210, 220, 240H2, 650 all went end of sale.
Starting release for the new SRX3xx and 1500 devices is 15.1...
Depreciation of features that were available in the now end of sale boxes without some kind of a way forward... don't know quite what to tell you here. Begin the conversation with your SE, maybe there is something "on the roadmap".