UnderRail is largely a combat game. So what you're suggesting for your build is a little weak, not because it's nonsensical, but because you don't have as much freedom to avoid encounters in UnderRail as you did in the old Fallouts, for example (well, aside from Tactics, obviously...) Let me syllogize you briefly. that's not really a word btw
Crafting results in greatly superior gear to purchased/found gear.
You want to minimize the effects on your character from a no-crafting build.
Therefore, you need a build that is not gear-reliant.
The most powerful non-crafting character you can make is a stealth psi character. Psi is heavily reliant on stats and skills, and only barely concerns itself with equipment. But you don't want psi, so what can you do to avoid relying on crafted gear?
You should probably invest in Mercantile. Mercantile will not only give you better deals on equipment, but it will also open up additional stocks in many shopkeepers, so you'll have more opportunities for them to have what you need.
You should probably invest in traps. Traps are easy to acquire (with good traps skill, they literally grow on the ground like weeds! Just pick 'em up!), cheap to purchase, and you don't need a whole lot of them.
As a corollary to that, you should look at Quick Tinkering as a feat. It may interest you if you decide to build into Traps skill.
If you want to find every hidden passage, you're going to need to put one more point in Perception, and you're also going to need to take the Snooping feat, and also carry the Perception-boosting goggles. 11 effective Perception is what you need. (if you use your suggested stat spread, you can put your first stat point into Per and you won't miss anything - the high Perception secrets come later in the game)
If you're willing to invest just 60 points into Chemistry (you need 69 effective), and 10 points into Mechanics and Tailoring, you'll be able to make your own grenades. Flashbangs, HE, frags, incendiaries. Incendiaries are immensely helpful and I suspect you could win the game on Normal using nothing but grenades and throwing knives. Maybe even on Hard.
If you plan on using traps and grenades a lot, you'll probably be avoiding melee as much as possible. Thus, you should invest heavily into Evasion and somewhat into Dodge. Escape Artist will be your friend since you won't want people to get into melee with you.
Interloper is pretty much strictly QoL. It's nice to have, but you don't need it. If you decide you're going to invest heavily into throwing, you *do* need to pick up Grenadier and Three-Pointer for grenades. You should also put a couple of the stat points from levelling up into Dexterity since that's going to make your thrown attacks better. Throwing builds are objectively weaker tier builds, and you need to get the most bang for your buck, figuratively (and literally, in-game).
I know you don't want crafting, but you seriously may want to think about getting 25 effective skill in Tailoring and Mechanics, or even 50 if you're willing to go that far. The reason for this is if you can craft your own repair kits, the game economy will be much, much more forgiving. Repairing items before you sell them increases their value. Repairing your own equipment will become necessary eventually and buying repair kits gets pricey, especially early on. Some merchants buy them, and their value is high and weight low. If you're on Easy or Normal, maybe it won't matter, but if you plan to play on Hard or Dominating with your already self-nerfed build, you really will find having a supply of repair kits (and grenades, as mentioned earlier) to be very helpful.
