Yes this should be possible. I think the main constraint would be keeping the cell chemistry the same so that OCP is similar. I've been playing with a pack model of cells with mixed capacity using another open-source tool in our pybamm-team collection https://github.com/pybamm-team/liionpack

That’s essentially what adding decoupling capacitance to a circuit does. All of this is going to be limited by the fact that without extra switching logic the entire circuit wants to be the same voltage, once your fast source drains enough, circuit voltage will start dropping and the source will begin sinking current as things balance.