When you receive a message as a string, you can turn it back to a number using the casting system expressions.
For example set dictionary value to float(multiplayer.message).
When you mention "ready-feature" are you talking about the "Is ready for input" condition ?
If not, this is likely something you have implemented yourself, right ?
Perhaps you should post your project .c3p file and explain clearly what you are looking to achieve.
This would be simpler to understand and diagnose what your issue is and provide help according to how your project is setup.
If you have suggestions for new features or improvements in Construct 3, we have a feature suggestion platform here which lets everyone vote on their favourite ideas:
Please look for existing ideas before submitting a new one. It's better to get all votes on the same idea than spreading it around.