Upload & Sell: Off
There are workarounds for everything, but every workaround is either time-consuming, money-consuming, and/or complication-adding (putting a pass-through device on the hot shoe tends to be a risky thing because it could break or have various intermittent connection issues). Putting on an ND filter involves added expense and time and another piece of delicate equipment to carry along for every wedding involving a daylight outdoor situation like that.
The workaround for using my phottix strato IIs after the trigger bases' plastic started snapping away from the main body was to use the pc sync ports and mount the trigger alongside my flash with a rubber band. This is not pretty, it adds a cord, and every so often the trigger slips off and falls down somewhere. It was best mounted on the camera as originally intended, but the structural flaw of the triggers prevents that. In spite of this, I'm pretty happy with the triggers because they are generally very reliable.
I don't ignore benefits (in the 5d3's case it's mostly the silent shutter mode), but I do scrutinize things fairly critically, especially when they are declared to be upgrades but do not "feel" or "function" like upgrades during 50% of the wedding day.
If any of us was completely satisfied with a tool, would we feel a need to upgrade it?
I feel completely satisfied with the 35L, generally satisfied with the 24L, 50L, 85L, 70-200 f/2.8L IS, 16-35L II, 580EX flashes, etc...
I am not completely satisfied with the 5d2 (limited focus system, bad shadow noise when pushed, etc.), 5d3 (focuses slower/tracks worse than 5d2 during receptions, terrible shadow noise when pushed), d800 (bad amp glow at higher ISOs), and 35 f/1.4g (seems to miss focus too often).
You might notice that I'm dissatisfied mostly with camera bodies, the things that are the most transient and subject to upgrading, and that have multiple different offerings available (in different price ranges) at the same time (e.g. 6d, 5d3, 1dx, d610, d800, d4, d4s, df), and/or some comparison (35 f/1.4g vs 35L).