Gents,
Having been involved with PW4 for a long while, it does depend on the platform as to how easy it is to integrate MIL-STD-1760 weapons. Harriers' integration did not use the full interface and was done fast and dirty. GR4 did use the recommended interface, and indeed got the weapon on in quick time, albeit not with a full release capability - I'm talking in terms of release sequencing and targeting..
The eternal problem has always been the tweaking of display software, allied with sytem platform computers to eke the most out of the weapon(s) deployed. The longterm stuff will get done in the background while UOR capability can be done quicker.
Large chunks of time/effort are spent examining weapon configurations that are suitable to be carried/released/jettisoned/operated with each other. Harrier stores management is/was a fairly groovy system in that it retained a mixed load capability second to none. Basically you can hang anything off it and the armament control computer wouldn't care. GR4 SMS is a bit more finicky and would have to be tested a lot more to generate a workable clearance.
Not being privy to Typhoons' workings (info was a news release - not tub-thumping), I can only imagine the super-computers involve in release and jettison of ordnance from a plane that is highly agile/unstable would involve a lot more work than throwing it on. For instance GR4 never needed the Flight Control System updated - even with 4 Storm Shadow slung under it. I would hazard that Typhoon does or the FCS is going to go potty with a new weapon/weight/drag on whatever pylon.