The draw back of convetional air tankers, is thier size - it effects their manuvarebality, and agility. Buddy Refullers (BR) do not have this limitation. They do not need to operate well within friendly skies. They are more effective in hostile conditions, than dedicated refullers.
They do need to carry an extra pod, that would weight about 600kg's, but they can still carry extra fuel tanks / EW pods, and A2A missiles.
What you have in the following pic, is an F18 Super hornet, with 4 external tanks, and a centreline refueling pod. This would come in handy, when a friendly a/c would be returning from a sortie, and low on fuel. This mini tanker could fly out, and make sure that the buddy had enough fuel to land safely.
He still has 2 wingtip, and two under wing hard points available for missiles.
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Now look at the configuration of this Rafale. The refuller seems to be carrying Mica A2A.
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This kind of capability, helps improve combat radius, and loiter time. It can safely operate in hostile environments, where traditional refullers would have a tough time, or would be costlier to operate.