In my opinion, Undercover Brella is a great weapon that can be used to hold down an area with Ink Mines and splat opponents with Splashdown, but there are still a few things to clean up.
To begin, I agree with what Yami Silver said about it, in which to remove the damage multipliers. However, I still think that the multipliers for the charger should stay the same because a Splat Charger would need to use 2 fully charged shots in order to break the shield, and by then, he or she is probably splatted.
In addition, I think that the ink consumption for each shot should be 2% of the tank, giving the Undercover Brella a total of 50 shots. To balance this, the shield should ink the ground as well which should keep the amount of shots the same. This would provide users a reason to not have the shield up all the time and would give some interesting new play styles to the weapon.
Plus, the damage for the Undercover Brella should become a maximum of 45 instead of 40. I find it hard to aim with this brella, so it mostly becomes a 4-shot splat instead of a 3-shot. People have suggested making the damage 50, but then it would make it a 2-shot splat like the Splat Brella. I think that if this happened, people will abuse the damage with the protective shield by camping (or sharking) by certain choke points.
Overall, there is great potential in this brella, but I feel that it is being limited by multiple factors. Although, Nintendo should be careful to not over buff the weapon like they did with the Splat Brella. This brella needs to keep its sneaking vibe in order to make it an enjoyable and interesting weapon.
Link to Yami Silver's video about it:
