>>"I am not talking about an overweight situation. Max weight and max T/O weight is not necessaryly the same"<<
Indeed they are not the same. Max T/O weight is linked to max zero fuel wt, which is a basic aerodynamic/structural limitation of the airframe. Exceed that, and you place lots of restrictions on the aircraft, including limiting g loading, bank angle, and AOA, critical parameters in any kind of maneuver. These limitations are severe enough that exceeding T/O weight requires MAJCOM approval. It's very rare for MAJCOM to grant that request, even in war time.
If you're going to hit a tanker on your mission, you do it mid-mission, much closer to the target area. You plan to fly to your prudent limit of endurance taking into account alternate landing sites plus some margin, and that's where you schedule your tanker rendezvous. Better yet, you fly into the target area with fairly empty tanks and plan on hitting a tanker on the way OUT.
But if every fighter had unlimited tanker support, no one would bother with increasing fuel capacity of fighters, and everyone is doing just that. The truth of the matter is that there are only so many tankers available to go around, and those same tankers also service the large transports (like C-141, C-17, & C-5 which take a LOT of gas) as well as large sensor aircraft (like AWACS and JSTARS) and other command and control aircraft, all of which are rising in numbers, and all of which are operating more and more forward into the battle area, and all of which take LOTS of gas.
>>"If you need to dogfight (Which by the way is highly unlikely in todays world.) you just drop your external loads."<<
If you dump your weapon load before reaching your target, the enemy has already beat you without firing a shot. That's the LAST thing you want to do. DCM (defensive combat maneuvering) calls for some very aggressive piloting to avoid getting shot down while reaching the target with your payload. And I'm talking here about ground fire as well as from enemy fighters, so aggressive maneuvers are NOT limited to air-to-air dog fight situations.