The Force's biggest issue is their attack.
When they actually show up, and make a fist of it (IE the Reds/Crusaders/Tahs/Chiefs) etc, their defence seems to be well organised, their breakdown work solid enough. THeir attack is just so unimaginative, its all based around someone making a break by themselves and then everyone just trying to support. There doesn't seem to be any purpose and intent when they have the ball. To fix this, I reckon they should throw everything they can at Phil Mooney as an attack coach. He always seems to get sides humming in attack and working as a cohesive unit. Just not a good head coach.
I don't know how to solve the fading at the end of games, but scoring an extra 10-15 points a game would certainly go a long way to fixing that.
For the Rebels, its just purely defence. They clearly score a lot of points, but just cant prevent letting in even more. To fix this they should be throwing everything they can (IE Beale's paycheck) at the Fainga'a twins. If anything in the world is going to fix a sides leaky defense, having Colby, Saia and Ant on the same side is going to do it.
The other thing they desperately need is a flyhalf. Not Beiber, not Beale, an actual flyhalf so that those two can play their own game out wide where they belong. Someone who plays like Matt To'omua or Johnny Wilkinson. Rock solid defender with a good tactical boot, who can run phases. Not an off the cuff running 10, a solid, hard tackling and well organised 10. With Beiber and Beale, they can run a lethal counter-attack when in general play, and score their tries that way. For the rest of the time though, they're really lacking in a good 10 who can organise the team and direct them around the field. Run an Eddie Jones' Wallabies style routine with 25 different set plays off the 9 and 10, and build pressure by doing that, and then let Beiber and Beale do their thing when the opportunities arise out wide.
And couple of decent props wouldn't go astray either.