The tub idea would be a rougher sight for someone to come across than it would be to see you with a self-inflicted gun wound.
When you shoot yourself, it goes everywhere. Blood seeps into the flooring beneath you. Deep. All the layers need replaced to get rid of what leaks out of you.
Your brains fly and land on every surface. Your head looks like a jack a lantern in the middle of November.
Now imagine that, but the body is partially dissolved in a bloody bathtub. Bits and bobs of yourself are floating in the solution around you. The stench would stay for weeks, maybe even months after you're found. It would be a way bigger mess.
I don't know how accurate this is in all areas, but I read somewhere that emergency services don't set families/roommates/landlords/etc with someone to do the deep bio hazard cleaning. That either has to be done by your next of kin by hand or they have to pay exorbitant amounts of money for professionals to come in and take care of it. Additionally, when I read that, I read that someone's family member decided to shoot themself in the backyard so that the mess wouldn't ruin the house they were in. I thought that was smart. I've been considering trying to ctb outside since about the age of 11 or so. Long before I read that. I always assumed that the instinct was just a "Hide-and-Die" type of response. Turns out it made the most sense economically and cleanliness-wise.
And now that I'm thinking about it, going for a hike or finding a mildly woodsy area to ctb makes the most sense because animals and worms and fungi and all that shit can reclaim you and do the clean up so no one else has to. Win all around.
I did read your response about not wanting your body to decompose. May I suggest shooting yourself near a fire pit or after setting fire to your car? Instant cremation, although the accuracy of the fire isn't guaranteed after you've shot yourself. This also sounds like something to do in the middle of nowhere.