Not via simple software means.
The GBA hardware setup and coding approach means it is maybe not as completely opposed to the notion as some things I could cook up but about as close as you will ever see in sensibly designed electronics.
It is possible on some older systems (or some games for them) because of some aspects of bankswitching, it is possible on newer systems with file systems behind them because it is just files and it is easy enough to redirect things there (it is probably what the hacked device is already doing for the likes of hard drive/USB/SD loading), the GBA however is the worst of everything here really.
To do it on a GBA....
The GBA has 3 locations where all 32 megabytes of space 99% of commercial ROMs use (
https://mgba.io/2015/10/20/dumping-the-undumped/ for the exceptions,
http://problemkaputt.de/gbatek.htm#gbamemorymap for the memory map used by everything else). It has two instruction sets. It is new enough that people could be using calculated pointers and others pointer maths extensively that might not show to basic static analysis (not that said static analysis is in any way easy to begin with).
Also on older systems you have a better chance of being able to find every random jump via more practical means if a given playthrough and few choice alternatives is likely to encounter them all -- for something as essentially random* as a lot of GBA games... please don't make me think of what that would take.
*the simplest code is often something like a conversion tool that goes through everything, does operations on every byte from start to finish and then exits, this is not games but a NES platformer wherein you play through 8 levels or die trying is rather different to something like megaman battle network where you have battles, minigames, alternative battle types, the ability to go to one of 10000 locations at essentially any point you like, reset, load a save... and even a 8 levels platformer on the GBA probably has a few oddities that the NES coders would not likely have done but were expected by this point as far as reset, level select, sound options, maybe some graphics options, link play perhaps, score tables, saves, bonus levels....
You would have to hunt down every pointer and change it, figure out every calculation done (in both instruction sets the GBA has), figure out every type of read to the ROM at every point in the game and make sure it is going where it needs to be, for every would be second game, also some means to select it but if you can do the former then the latter is trivial and you could probably do that with a cheat simply enough. Devs with source code to the games could do this easily enough (it is why we saw all those ? in one titles later in the GBA life, most of which were not exactly million selling titles in the first instance). Indeed say you wanted the Advance Wars games bundled I would grab that Japanese double pack and probably translate it from scratch (not just port the more than acceptable existing English scripts, whole translation from the ground up) sooner than trying to merge the two US ROMs.
When in every previous instance this has been contemplated then "buy a better flash cart", "get a better emulator" or "the piece of hardware you are trying to play this on is clearly a piece of junk, get something better" has been the simpler solution...
kinda like how the super card sd works 
