I have been muddling this over for a while. I think some weapons need an Attack Speed bonus instead of Charge Time Reduction. This opens up the arsenal of weapons to not have a charge but instead allow the player to attack without stopping. (Fast edit: weapons that attack in this fashion deal no increased damage.)
Examples I can think of:
Fast guns (the auto gun line, antigua line, and the chilling duelist)
Fast swords (red saber, cutter line, flourish line, and spur line)
The best way to balance this out is by putting a cap on how long you can do a constant attack.
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Its late, I will update and edit this as ideas cone to me.
I have a few concerns about this.
1. I believe you are talking about when a weapon gets to Level 5, it gets CTR Low. And you wish for this to be ASI Low instead.
2. ASI is somewhat like a luxury. Allowing for people to get ASI too easily is just boring.
3. With ASI being available to all weapons, there won't be any variation after as many would just get heavy swords.
The meta with this suggestion would be: Heavy swords > ''Toothpicks'' (BtB,FF)
Heavy swords are suppose to be about damage with a setback of attack speed.
'Toothpicks' are about quick attacks to deal medium damage.
A few other concerns also include gun spamming in Lockdown. Although ASI may be great in all ways in the clockworks, in Lockdown, ASI just encourages spamming (including the Polaris line).
''Fast guns (the auto gun line, antigua line, and the chilling duelist)''
ASI isn't actually really needed on these weapons (except Autogun-line) due to their already quick speed and so it is unfortunately quite useless.
''The best way to balance this out is by putting a cap on how long you can do a constant attack.''
1. OOO would need to rework every weapon individually with this feature of ASI instead of CTR.
2. It could take the fun out of quick and speedy weapons like the cutter line if the number of attacks was limited.
Hopefully you don't take it personally however you may need to think harder about this feature of ASI instead of CTR before it's flawless.