That's why I mentioned the first actionable/possible action. Wrong target type (between PM/friendly/nonfriendly)? Target dead? Target out of range? It'd then check the next action macroed and use the highest of that list. Note that even regular actions do this, such that the range we can pull off an action from can be well above our actual "maximum range", given sufficient difference in position between when the action was checked and when it appeared to go off.
And again, the idea is simply to strike a balance between what behavior the devs want to forbid (e.g., auto-play or PvE combo consolidation... beyond the ones they already consolidated) and what they allow, un-neutering just whatever seems to be the intended uses of macros.
Yes, we can already use a Dia/Regen macro to make it so the button is of use regardless of target type, but we sacrifice queuing to do so. Given that we CAN do that through the macro with just a bit more timing or button-mashing, though, it seems well enough intended to be functional that the devs may as well let that be queued.
On the other hand, something like a <wait> macro using decimal seconds or %GCDs is not at all decently possible, while combo-in-1-button macros rely on the clunkiest of gimmicks and disused hotbars to draw from. As such, they seem wholly unintended, and so I wouldn't bother asking for what all would be necessary to make them function properly.
