Without knowing exactly what you are working on, here are a few ideas:

1. Figure out if you can do fewer slow iterations. What's driving the need for a full PCBA run for each iteration? Might be able to split out to rigid assembly and flex for example.

2. Run more experiments in parallel. If you have multiple ideas or variations to test, design them all and fabricate them all. Flex antenna? Make like 30 parametric variations.

If design then becomes the bottleneck, then automate that next.