Yeah, a major problem with FFG's system, which kinda breaks the whole narrative/cinematic thing they aim for, is that there's no mechanism for opportunity attacks. It can be added through house rules, of course. I haven't added it to my own game(s), yet, because the situation has yet to come up. In this game it's now come up twice. First with the morons exiting the command bunker (had such a house rule existed then Tasha and Rath would have been able to save poor G2 by reacting to the Imps in lieu of the pilots attacking at the top of the turn), and now again with the Imps unable to shoot the cam-bots despite waiting anxiously for anything to appear so they could shoot it.
FFG has gone "rules lite", and left much for GMs to fill in, if they choose to do so. To me, having to stand by and do nothing because the RAW has no "reaction action" or "reaction maneuver" breaks immersion. Yeah, not having such a mechanism makes the game considerably simpler, but it does exact a price. Having the cam-bots frantically backpedal to avoid coming under fire is cinematic. It is equally cinematic to have them reveal the ambush by getting suddenly shot at (which is what the PCs were expecting/fearing, precisely why they sent droids in first).