If the electronics are c. 20 years old it will probably be impossible to buy any identical additional systems.
Whilst the airframes should not take long to deliver, depending on the state/queue length of the production lines involved, the USAF has to set up a complete logistic support arrangement for the Wedgetail, or ask UK and/or AUS to expand theirs, before they can bring the thing into service. The proposed timescale looks reasonably difficult for that.
That said, it does look like another opportunity for a programme Charlie Foxtrot. One would hope Boeing, DoD and USAF will have some top-notch folk in the management team, and that the pork barrel will be well hidden.
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