Thrown weapons in GURPS are in a bit of an odd spot. They get all of the disadvantages of melee (short range, relatively easy to defend against, weight of the weapons) and ranged (range penalties, reloading/getting a new weapon, and weaker All-Out Attack options).
One change you can make to GURPS that wouldn't disrupt it too much would be a special combat option. If you elect to make it a Technique, it would be Hard and max out at Prereq-2 (it should always be harder to throw at maximum power at the expense of accuracy, otherwise it's just an always-on damage bonus.)
Harder Throwing - A muscle-powered thrown weapon can be hurled with maximal force, trading off accuracy for damage. This gives a -4 to hit, +2 damage or +1 per die. In addition, add +2 to ST to determine half-damage and maximum range. The thrower must make a DX roll after releasing the weapon; failure means you are off-balance and cannot do anything until your next turn; critical failure means you fall down! Can be used with All-Out Attack, Attack, Committed Attack, and Move and Attack.
Can you stack this with Telegraphic Attack? Not normally, because it's a thrown weapon. But if you allow it (an obvious windup and throw), it would net to +0 to hit, +2 or +1 per die to damage, +2 to defenses, DX roll not to fall down. Stacked with AOA, it would be +1 to hit and the effects I just listed (or -3 and the damage, etc. effects without Telegraphic.
Great for that all-out chuck of an axe or hammer or rock to break something.
Another way to do it is to essentially allow it to straddle melee and ranged for All-Out Attack and Committed Attack.
All-Out Attack - Muscle-powered thrown weapons can use the following options for All-Out Attack:
Determined - Make a single attack at +1 to hit.
Strong: - Make a single attack at +2 or +1 per die to damage, whichever is greater. Also adds +2 to ST to determine range.
Double - Throw two weapons, one from each hand, or Fast-Draw a replacement in between. If the Fast-Draw fails, your turn ends immediately, and you must take a Ready action next turn.
Feint - If using Ranged Feints (see Tricky Shooting, GURPS Martial Arts, p. 121), you may use this option normally.
No other AOA options are available.
Committed Attack - Muscle-powered thrown weapons can use the following option:
Strong - Make a single attack at +1 to damage (or +1 per two full dice of basic damage, before other modifiers. Add +1 to ST for purposes of determining range.
Like a melee attack, the character may make a second step at -2 to hit. Active defense penalties are normal for Committed Attack (GURPS Martial Arts, p. 100).
Defensive Attack - Muscle-powered thrown weapons can use Defensive Attack as written. In addition, the attack has -2 ST for purposes of determining range.
Overall, I think that's an fine way to split it. You aren't able to access the full AOA benefits to hit, because you can't have them now. But you can throw harder, throw as hard as possible, or throw quickly and without sufficient force to stay more defensive. And we cover how to use Ranged Feints with hurled weapons. I threw in the ST benefit because it seems like range should be affected, and it's in line with the ST benefit based on Swing.
The combat option is just a way to do this as a special choice without changing any of the attack maneuvers. I probably wouldn't do both of them, or you can get some silliness (-3 to hit, +4 or +2 per die to damage, etc. without any real ability to get there with melee weapons.) But I thought it up and I figured I'd share.