I haven't done too much with shotguns beyond theory crafting as I usually drop shotgun characters quite quickly.
As someone who enjoys high mobility, I would say it is fun to be able to leave your enemies in the dust as you skip between them and it's definitely worth a go over plodding around in heavy armour.
As for the level 30 build, it's not very well optimised, which dominating will punish you for. Some things you should definitely have a look at:
-Perfect Scattering is a pretty shit feat and not worth taking
-With your level of Dex, you won't get a great deal out of Three-Pointer unless you invest heavily into throwing. If I were you, I'd take a point out of Int and two out of Dex and put them into Agl instead to get Expert Sprint. Taking a point out of Int won't reduce your psi slots and the only feat you get from it is Gun Nut, which isn't particularly spectacular, having five Dex will still allow you to get Leading Shot
-I believe that the effects of Barrel Stare and Leading Shot are mutually exclusive, so you may want to pick one or the other. Leading shot is good as Dominating enemies have lots of evasion and it'll help you land shots even with relatively low Per. Not sure exactly how low a Per score you can get away with when you take leading shot, you'll have to ask someone who's played with it or find out the hard way.
-Grenades can really bolster your power at low level if you're able to craft them as usually the best you'll find before Depot A are of the Mk. II variety, and in small numbers. By level 7, if you invest fully into chemistry, you can make your own Mk. IIIs. You only need 69 chemistry to create Mk. IV frags, which is a pretty modest investment for a great deal of power. Mk. IV frags aren't sold too commonly, especially not in the early game, but you can save up plenty of money for them on Dominating if you know what you're doing.
-Your lockpicking and hacking skills are way too high, you won't see many locks above 130 difficulty (if any) and you can boost your effective skills quite a lot with items. Crafting skills are too high as well, especially if you're going to use intelligence-enhancing drugs and/or workbenches.
-Suppressive Fire works very well with Opportunist, you should get both feats early on.
-Sixth Shell is pretty ridiculously powerful, I'd nab it before Hit and Run as you likely won't be killing many enemies per turn early on anyway, and 25 MP is not very much.
-More mercantile points are definitely a good idea, 105 effective points will allow you to get the best goods from all merchants, especially the ones selling high-tier shotgun frames.
-Good specialisation points are Blitz cooldown (you can get it to cooldown pretty quickly if you also use Limited Temporal Increment), Sixth Shell, Hit and Run if you want to be really mobile and Leading Shot if you want to almost entirely ignore enemy evasion. Should you get (Expert) Sprint, infused cave hopper tabi will help it cooldown nice and fast too.
-13 Agi to get Expert Sprint might not be worth it in your opinion, as you can only get it quite late in the game. You might want to keep Agi at 10 and redistribute the points elsewhere, such as 2 into Str and 1 into Dex in order to get Grenadier and Full Auto, though I personally don't tend to bother increasing secondary/tertiary base stats unless doing so would unlock new, good feats for the build.
-Even if you keep your Str at 5, you can still always use Rathound Barbecue/Rathound Regalia to up your strength enough for wielding combat shotguns temporarily if you so wish.
That's about it for my first impressions, anyway.
As for finding a shell strap belt, I think that's just luck of the draw as it's not a special item. Your ideas for other feats are not vital in the case of Pack Rathound and Interloper; Premeditation and Grenadier could definitely be of use to you, though.
