Since he said assault rifle + quick tinkering + traps, I'll suggest this build.
Level 1
https://underrail.info/build/?AQYGBgMKAwYPDwAAAAAPDw8ADwAPDwAAAAAAAAAAADkm378Level 4
Dex+1, traps 25 for tinkering
Electronics 25 for taser
Chemical 30(effective 35) for MKII frag grenade
https://underrail.info/build/?BAYHBgMKAwYeFAAAAAAeHh4AGRQZHgAAAAAAAAAAADkmOzDfvwLevel 8
Str+1 for full auto
Throwing 30 for grenadier, dodge 30 for escape artist
Effective hacking 58(and will be 60 at level 9), effective lockpick 48+7 from jack knife=55 for depot A.
Start putting point into tailoring for siphoner leather armor, mechanics for crafting rapid 7.62mm hornet.
Effective chemistry 50 for MKIII frag grenade and flashbang.
At level 9 or 10 take psi pill and TM 35 for Limited Temporal Increment.
https://underrail.info/build/?CAcHBgMKAwYyHgAAHgAoMiEAGTIZKwAYAAAAAAAAADkmOzAWFd-_Level 12
Per+1, TM 55 for Psycho Temporal Contraction.
Get SGS Tattoo
Start putting point into mercantile.
https://underrail.info/build/?DAcHBgMLAwZGKAAAHgAyMiEAGUYZKwAyAAAANwAAEzkmOzAWFStOSsOM378Level 16
Per+1, effective biology 50 for focus stim.
Effective mercantile 92+3 from underpie will allow us to gain access to second tier of merchandise of all merchants(except Hanna)
https://underrail.info/build/?EAcHBgMMAwZaKAAAHgAyPCwAGVoZMCQyAAAANwAATTkmOzAWFStOSsOMScKH4qeqAd-_Level 20
Per+1, effective mechanics 115(with workbench 132, hypercerebrix + workbench 150, all-in + hypercerebrix + workbench 179)
Start putting point into electronics for better energy shields and goggles
Effective chemistry 69 for MKIV frag grenade
TM 70 for Stasis
https://underrail.info/build/?FAcHBgMNAwZuPAAAHgA8QTMALWFKNyQyAAAARgAATTkmOzAWFStOSsOMScKHTwLio7EC4qeqA9-_Level 24
Agi+1, Stealth 80 for blindsiding
Effective hacking 105(with Lemurian Engineer Suit + Huxkey 130)
Effective electronics 124(with workbench 142, hypercerebrix + workbench 163, all-in + hypercerebrix + workbench 194)
Effective biology 61(with workbench 70 for crafting hypercerebrix)
https://underrail.info/build/?GAcHBwMNAwbCgkYAAB4AUFBBADBhaTcsWQAAAEYAAE05JjswFhUrTkrDjEnCh08CKsKF4qOxAuKnqgPip7QE378Level 28
Effective throwing 123 for maximum accuracy(10 tile 90%)
Effective lockpick 98 + 7 from jack knife + 10 from Lemurian Engineer Suit + 15 form Huxkey = 130
Effective traps 96
TM 148(effective 135) for reducing reversion probability of PTC
Mercantile 87(effective 103) will be effective 140 by taking all-in and hypercerebrix, which will allow us to get 20000 charons for selling Reef Glider
https://underrail.info/build/?HAcHBwMNAwbClmEAAB4AWlBBAD9haTcsWQAAAMKUAABXOSY7MBYVK05Kw4xJwodPAirChcK14qOxAuKnqgPip7QH378Level 30
Pack rathound and interloper for QoL
https://underrail.info/build/?HgcHBwMNAwbCoGEAAB4AwpVQQQA_YWk3LFkAAADCnwAAVzkmOzAWFStOSsOMScKHTwIqwoXCtScd4qOxAuKnqgPip7QH378