I feel like WM in its current implementation is a ton more movement-forgiving than Sniper Training, and I prefer it that way, but I certainly wouldn't mind something a bit more fluid, less jarring on acquisition, and less of a dps loss prior to getting Iron Jaws. At level 54, you've about 500 potency of AAs to make up for every time you pop WM because of the 15-second lock-in. On average, each GCD would need to deal 266.7 potency to break even via the 1.3x damage modifier, reduced with skill speed (since SS does not effect AA damage or frequency). The recent Bard buffs make WM more necessary for each DoT, but have done nothing to change its lackluster effect on filler damage (the bonus 45 Heavy Shot potency falling behind the average 80 potency of AAs done per 2.5s GCD).
The most casual (or smoothest but potentially least interesting) side of this would be to simply allow any attack to charge at 10% per half-second, scaling with skill speed, to a maximum of +30%. Can fire early via movement, but oGCDs will otherwise queue for after the full charge time. Or even limit this to primarily direct-damage abilities like Heavy Shot, that look like they might actually benefit from a physically empowered shot at a much higher maximum bonus. Your spin-y Windbite shots and the like stay instant. Can pre-cast the charge before selecting an enemy or using the ability via the ability itself, rather than it being a toggle. Replace the animation with what looks like spiritually empowering and slightly extending the bow.
Alternatively, you could then attach something like Sniper Training atop that, such that charge bonus increases (from say 3.33% per half-second to the 10%) with time spent stationary to a maximum of 6 seconds, and you'd then have a very similar immediate leniency to Sniper Training without giving free rein to movement, albeit perhaps at the cost of its current stutter-stepping and Feint/Straighter Shot/WM-Drop movement style.
Probably mostly by nature of it actually being a projectile there, rather than something that just spontaneously erupts from the target itself. On top of looking great.