Unfortunately your work-around can't be applied because the issue happens for every articulation, not only for the staccato. In addition, it would not affect the midi output of the articulate script.
Note that the issue is not on the staccato dot, it is on the gap between the accidental and the bracket. What is faulty is the second bracket, not the first one.
I just verified that TupletBracket has the outside-staff-priority set to ##f as default.
If I give it a value, the brackets result aligned:
%%%%%
{
\time 6/4
\override TupletBracket.direction = #UP
\override TupletBracket.outside-staff-priority = #1000
\tuplet 3/2 { a'' a'' ais''-. }
s
\tuplet 3/2 { a'' a'' ais'' }
s
}
%%%%%
However, this messes up slurs, because it won't be possible anymore to put the bracket inside them.
I think that there are two issues at the same time on the calculated TupletBracket.padding:
1) the upper margin should be calculated from the BOTTOM of the TupletBracket
2) the lower margin should take into account every visibile accidental
Let's hope there's at least a work-around for this, I think it is very important.
Cheers,
Paolo