A simple rework that would both revitalize this perk a little, and rid perk pools of the highly undesired (and quite useless) Multikill Clip would be to simply combine both perks into one, with some slight tweaks.
Here's how I would change it:
• Rename the perk to Kill Clips
• Reloading after kills boosts damage, based on the number of kills
• x1=25%, x2=37%, x3=50%
• While the perk is active, decreases the number of kills required to advance it to the next tier
• eg, at Kill Clips x1, landing 1 kill (instead of 2) and then reloading will grant Kill Clips x2,
• Removed MKCs override, and allows the highest tier buff to persist upon reloading after a kill (though perhaps it should reduce the perks total duration by 0.5-1s after each reload if balance/perk competition is a concern)
• Adds a hidden Reload Duration Multiplier that scales with stacks held (each stack increases reload speed)