Yes, I just don't know what will be the best solution.
1/ Either use half-float for the render target (would help color clipping)
Pro => it can be unclamped (be outside of [0:1]). So you can still use the blending unit.
Pro => support primitive that overlap
cons => need a 2nd pass to clamp/wrap the result
cons => bandwidth requirement for big upscale
cons => interaction with texture cache
2/ Either use a FS blending (require GL4.5 extension)
Pro => easier to implement (still use standard render target)
Cons => need to split draw call in non-overlap draw calls
Cons => more FS power requirement for big upscale
It boiled down to the number of time those blending effect are used and how game designer make them (single big sprite (like GTA) or lots of small triangles).