According to the Steps of an Attack, step 4 is
4. Apply Modifiers: If players have any effects that gain or remove icons or Accuracy, they are applied at this time. This includes spending evade results to remove surge results. Any surge results that provide modifiers are not resolved until step 5.
(RRG, p5)
Technically, the rules don't specify how to resolve several such effects, so it could be argued that they must be applied simultaneously and therefore each ability's effect can only be based on the icons rolled on the dice, and not any icons added (or removed) by other abilities.
But I have always interpreted this to mean that any such abilities can be triggered sequentially in the order of their owner's choosing, such that icons added by one ability can be used to trigger other abilities. In this interpretation, if Han Solo were attacked while adjacent to C-3PO for example, the Rebel player(s) could apply C-3PO's Distracting (+1 evade for adjacent friendlies) first, and then apply Han's Cunning (+1 block per evade) next for an additional +1 block from that evade (plus any other evades rolled on the dice).
But there could still be cases where the order of resolution has an effect on the outcome, and it's not always clear to me which of these sorts of effects would be considered "mission rules" or "Imperial/Rebel effects" or "attacker/defender effects" etc.
Some more hypotheticals:
If a Rebel is defending and has a Combat Coat (convert 1 or more evades into blocks) but is also Weakened (-1 evade), could they convert all of their evades first so the -1 evade from Weakened has no further effect?
If Han Solo is defending while Weakened and rolls 1 evade, can he trigger Cunning for +1 block before Weakened takes away the evade?
If there is ever a way for Jyn to gain the Cunning ability, could she use Roll With It (convert 1 or more blocks into evades) and then trigger Cunning (+1 evade per block) for a net effect of +1 evade per block?
If Gideon is attacking and has Military Efficiency (convert 1 damage into surge) and also Weakness Revealed (-1 damage), or if he's wounded and Old Wounds (-1 damage for wounded heroes) is in play, and he rolls only 1 damage, could he choose to convert it first? That would leave him at -1 damage, but if he could surge for +2 damage it would still be a net gain.
If Gideon is defending and has Military Efficiency (convert 1 block to evade) and also Weakness Revealed (-1 block) and rolls only 1 block, could he choose to convert it first? This might be different from the above, since timing conflicts in combat go to the attacker first.
If Verena is adjacent to a defending Nexu who rolls 1 evade, could she trigger Create Opening (-1 block or -1 evade) to remove it before the Nexu's Cunning gives it +1 block? In this case Verena is neither the attacker nor the defender, so would the Imperial decide? Or, since Create Opening can be triggered "while a hostile figure adjacent to you is defending", could she choose to invoke it before dice are even rolled? In that case it wouldn't even matter if the Imperial interrupted to trigger Cunning first, since at that stage, there would not yet be any evades rolled to trigger it with.
Ultimately what I'm trying to determine is if there is ever a situation where an icon-dependent ability (i.e. +1 X per Y requires a Y, convert Z to W requires a Z, etc) might be triggered (whether preferentially or forcibly) before a flat modifier (i.e. apply +Y to the results, apply either -X or -Z, etc). Or can I assume that all flat bonuses/maluses will take effect before any other abilities that might be influenced by them?