wouldn't be actually easier nowadays to build a 3ds by reverse engineering it and make it compatible with 3ds flashcarts? or even just using the sd card slot? just a noob-theory, I know. I heard there was actually a person who was planning to reverse engineer the thing.
Same thing.
You might as well be saying "Why aren't the sword people thinking of ways to swing the sword through the air and have it collide with flesh in order to cleave through it with the result of crippling or killing the person on the other end?"
Reverse-engineering parts of the system involves studying how it works, and modifying it to work with flash carts and crap would require hacking/modding the system to change it's behavior. Aiming the stuff at the use of flash carts won't make it easier.
Just a question involving the encryption. If part of the aes encryption was somehow found, say the first 4 bytes or whatever, would that partially uncover any data or plaintext?
Nope.
why not just make a Mod Chip?
'Cause they'd still need to know how all the signals pass around the system (from what we know some of it's encrypted even when passing between the parts) and then how to modify them in order to introduce wanted behavior.
In addition, softmods are heavily preferred to hardmods nowadays, especially in mobile devices. When's the last time you saw somebody do a hardmod on an android phone to root it? How many modchips do you see for the Dingoo and Experia Play? Jack shit.
Hardwiring is usually better than softmods in the console world.
Not in the modern handheld world. There was one modchip for the PSP for examples, and almost nobody gave a shit. Why would anybody spend lots of time and money taking the device apart just to have a more limited version of what other people could do with just the purchase of a game?
they should be looking at more complicated means to get homebrew on 3DS,
Who says they aren't? There's pictures circulating of dismantled machines hooked up to debugging boards... and the people doing that shit aren't the people here asking extremely broad questions.
including de-soldering the CPU and wiring in a custom programmed CPU.
Hahahahaha, yeah, good luck with that nowadays.