Julian,
The BB60A will need firmware version 5 to be compatible. You can download it here: https://relatedcontentdemo.kinsta.cloud/support/product-downloads/bb60c-bb60a-downloads/
The TG124A being used as a standalone generator, and amplified/modulated appropriately, should probably work for immunity testing. Depending on your needs, you may wish to low pass filter the TG output as it tends to have higher harmonics than a dedicated signal generator. You would probably want to automate it using our TG standalone API, which you can get from https://relatedcontentdemo.kinsta.cloud/products/usb-tg124a/