Is it a muscle memory issue? Most of them are. Many can work fine with it. Heck, I could even work fine with Godot if I had to. I might even find working with Unreal okay given some time and getting paid appropriate (mental and nervous system) damages. 
If I recall correctly, Blender has these configuration that let you work the same ways as in other modeling tools - within limits of course, but at least keyboard shortcuts and whether left or right selects and so forth should match.
Did you check the Asset Store? There’s at least uModeler, and there are likely others. Not sure if any one of these follows a given established workflow but worth checking out.
I don’t think Steam is the right place for it. People will be like: “Uh. Why is that $10 when I can have Blender for free and do a lot more with it?”
Even on the asset store it will be a hard sell for the same reasons, and because of uModeler which practically monopolizes the “modeling within editor” niche, with ProBuilder taking a part in that too (and maybe Polybrush though that’s now legacy).
Still, if you want to see what the demand is, wrap it up and publish it. 
Just don’t do it “half-assetdly” because those comprise most of the store’s “editor tool” assets. In that case it’ll almost certainly won’t work to get past the $100/month threshold. You either WANT to make it happen and it shows and that entices early adopters, or it will show that you don’t lean into it, which means barely any sales.
Honestly, I think asset devs should do more open source. Promote it while it’s free, which means more likely to find early adopters. And when it gets more and more popular either you can pull the free version and publish it, or you split into free and pro, or you find other ways to monetize ie add-on packs, extensions, or just donations, sponsors.
Well, it’s a Unity asset with editor integration so it can only be for Unity devs.
From what you said, your potential target audiences are:
- Non-dedicated Maya users also working with Unity who are dissatisfied with Maya’s pricing
- Unity users who are also modelers looking for an in-editor modeling tool that works like Maya, because it’s the one they liked the most (but may not use due to cost)
- or: same as above, but just like you they are unhappy with Blender, and don’t like uModeler nor Max
So this looks as if there is a potential niche but it’s likely going to be rather small - a subset of modelers who are cost sensitive, not primarily modelers, and won’t use Blender for whatever reason.
as it is butter smooth.
