The Sinclair Spectrum port of Elite did something like this in the tape loader where, while loading off an audio cassette, it would load a new tape loader code

The Sinclair Spectrum port of Elite did something like this in the tape loader where, while loading off an audio cassette, it would load a new tape loader code and jump into that, and the load a bit more of the game, before grabbing yet another loader, and so on; it was a pretty effective way of stopping people getting to the game code without extra hardware.