I'd question installing a flight refueling probe on an RAAF Canberra. The RAAF didn't have any flight refuellers available before their acquisition of ex-QANTAS 707s in 1988, So, unless you want to purchase some flight refuellers as well as updating your Canberras, they won't be doing much refueling while flying.
The money saved on upgrade vs the purchase, infustructure, training of a new strike aircraft - be it A-5B Vigilante, TRS.2 or TFX will undoubtedly leave the Australian government/RAAF with money for a proper and sensible air refuelling tanker fleet to support the SLEP Canberra's. Add to this the reality that such a tanker fleet, no matter how small, will be utilised by other RAAF/RAN assets. Add to this even further, the use of airborne refuelling tankers will add to the points of the compass that SLEP Canberra's will be able to attack given targets - circumnavigate around known air-defence threats, etc...
In fact, I'm sure someone in the original forum I mentioned earlier suggested modifying some of the Canberra's to act as surrogate airborne refuelling aircraft, so as to support the 'strike' SLEP Canberra's to their targets - aka Douglas A-4 Skyhawk buddy/buddy system like!!
I'd much rather go for updated engines, more avionics (ie radar, ECM) and new guided weapons (Exocet. Kormoran, Penguin, RB04)
Granted, the updated engines, avionics and weapons will be a must!!
I'm wounding if it would be feasible for GAF to build and graft Canberra B(I).8 forward fuselage and cockpit to the existing RAAF Canberra's? By doing so, increasing crew operability, comfort and safety .....
M.A.D