Rebels don't reposition well but they do synergize well. So stop trying to make them do what you want them to do and let them do what they do well. One of my personal favorite lists uses a U Wing and Braylen Stramm and you just park in a corner and zero stop with the U Wing and position the stress machine behind. Stramm does greens and clears his stress bumping to stay behind. Arcs spread out to cover almost all approach angles.
Another of my favorite current Rebel builds uses Kanan, Determination Biggs with Rex and Jan Ors crew. It's really hard to hit Biggs when he's sitting behind a tac jammer with an Evade and Focus x2 (Jyn Erso) and I can remove two of your red dice.
I think Rebel list crafting is tougher than the other factions (it likely has been for a while) but some outside the box thinking and playing can yield great results. As evidenced by the whacky Range 3 Ghost/Ashoka list. Step outside the box and outside your comfort zone if you want to play Rebels.