This is a rather simple suggestion of adding the color option Onyx to the per-existing Tail marking.

The truth is I want to make a lion that looks like a least weasel. I was attempting to create a lion that looked similar to the least weasel decor only to find that there are no markings that make the tail dark enough to match the weasel without covering the entire body of the lion. I feel that the Tail marking would work perfectly, if only it was a little bit darker. There's only three color options as of right now: henna, black, and brown. None of which create the desired effect I'm after.

I looked up to see if anyone else had suggested this previous and found only one post in regards to an Onyx Tail marking - from 2014. Which can be found over here. As you can see it had quite the bit of support!