Beyond a certain smallness threshold it might also work to constantly swap in the models in and out of memory, but doubt that's a great experience to build on top of.
If your product is "good enough" with the current generation of models, you could cut OpenAI/Anthropic/Google out of the loop entirely by using open source & low-cost models.
Say that you want to translate a string from English to language X. Models A and B, having fewer parameters to spare, have less knowledge of language X. Model C, a larger model, has better knowledge of language X. No matter how A and B collude, they will not exceed the performance of model C.
It's not the completely same spec requirements though. When using an alloy, you would need to have double the disk space (not a huge deal on desktop, but for mobile), significantly higher latency (as you need to swap the models in/out between every turn), and you can only apply it to multi-turn conversations/sufficiently decomposable problems.