Essentially time and cost? Building such a Frankenstein-Phone would probably take you half a year to design the PCBs, get all the connections and power rails right, all the needed peripheral electronics for the chips. Read thousands of pages of datasheets to place the correct capacitors for the oscillator of the … sensor on your mainboard design. (And there are a lot of tiny components in a phone that all work together, in part depend on each other, or require additional control/supply circuits.) You’d need a lab and equipment do build it, and the mechanics and encasing. And probably some takes and failed iterations. And software and drivers also have to be rewritten and patched.
So I’d say if you have the expertise in electrical engineering, hardware design, embedded software programming… A 5 figure(?) sum of money for supplies and equipment and nothing to do in the next year… I’d say nothing is stopping you 😆
Right. I mean these things are really complex, usually not made to be repaired (i.e. modular) and lots of things are purpuse built to fit in that small form factor. Components are scattered around because there was some space left somewhere on a PCB and some components share a purpose, which makes it difficult to entangle the electronics…
And it’s always difficult to compete with mass-manufactured products. I like to tinker with electronics or build things at home. I learn a lot of things while doing it. And I get things that are unique and built spefically for my purposes… But usually they’re not cheap(er) than mass produced products, because I don’t buy supplies in bulk and it takes me days to build one thing while a production line can pump ot thousands of devices in the same timespan.
And I ocassionally repair (household) devices or just take apart broken ones for shits and giggles… And some of them immediately look like they just aren’t meant to be repaired or modified. Some components like a phone screen, camera or even the backlight or power supply of a broken flat screen TV can be messed with. But it usually ends with complicated PCBs. You can replace broken components (if you got the correct tools), but you can’t really change much about them without going through an laborious process of reverse-engineering and maybe designing a whole new PCB (from scratch). Which makes sense for smaller projects, but it’s just not feasible for complex devices like phones/laptops/TVs that aren’t meant to be repaired. Or where every design choice contradicts serviceability like with phones and cramming everything into the small slab.