Considering you are suggesting 9th and 10th drones that are bought by credits, this idea has already been suggested before. In the future, please search the forum to see if your idea has already been suggested before you post it. This helps to prevent the forum from becoming cluttered with duplicate threads and allows the developers to more easily see which ideas are the most popular.
Here is the link to the older thread: 10 Flax drones.
Feel free to go there and add your thoughts/suggestions for changes such as 2 slots rather than 1.
Have a nice day!