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I can bet that in such a game people would find one, two, maximum four viable builds and roll with them. Happened before.
Happened where? I've never seen a game based mainly on invention and crafting fail. Haven't seen one succeed either though. Just... haven't seen one.
Umm, this isn't sarcastic or anything, but can you recommend one? No matter how broken the game, I like playing mad scientist.
And as for the often-held idea that "customization makes things inevitably worse because it can't be balanced"; real life posits a counterexample. Remember, not all weapons in real life take the same amount of time and materials to kill someone.
A rocket launcher is far more deadly than an assault rifle in single combat (two guys in Kevlar quickdraw and scramble for cover at medium range, who is in worse shape after five seconds?),as well as being relatively cheap and simple to manufacture (I'm talking about unguided rockets) compared to high-pressure automatic weapons; but there are reasons that in a modern military you will find one, maybe two rocket launchers in a group using at least six or seven assault rifles. They are easy to miss with and you can't carry 200 rockets. They kill things you didn't want to, sometimes yourself. They get stuck in doors sometimes!
Titanium alloys (among some other blends) can be made rediculously heat resistant and undeformable; but they make up only a tiny minority of our technology. High scarcity, vital use in other fields, and certain situational drawbacks inherent in what gives them strength (they are inflexible, conductive, etc.) makes their use a values judgement.
While I agree that shoehorning in customization where it was not well thought out can break competitive balance, the concept of "technology" works somewhat different from normal balance. In permadeath (or just very high equipment/structure/posession damage relatively open PVP) environments, like some kind of scavenger world, while "better" equipment will probably exist, it will be contested so highly destruction becomes a real possibility. If you take something fancy into combat, it is going to attract bullets/lasers/fireballs/thrown knives covered in acid. Some will probably hit it. When it breaks or gets stolen, it probably won't be as easily replaceable as something less "better"; unless the laws of physics in the universe in question are very poorly designed.
Building a deathray that can often oneshot someone is an accomplishment.
Keeping that deathray when everyone around you both wants it and fears it is a much bigger challenge.
Mass-producing deathrays, keeping them fueled/maintained, and deploying them successfully when everyone knows they exists and the basic principles of how they work is a nightmare. More so once people start experimenting with deliberate counters.