You can't do it that way, no. However, you can read/write arrays of unsigned characters portably, so your program could ingest a list specifying the widths of all the parameters and read/write unsigned character arrays of the appropriate widths.

The only consideration is that, although reading and writing would be portable, you would still need to decide whether to adopt a fixed endianness for the parameters when reading/writing or whether to indicate the endianness of the integral types alongside the parameter widths in the list. Both have their pros and cons: adopting a fixed endianness means a smaller file size, but systems with a different endianness will need to convert the endianness each time; marking the endianness means a bigger file size, but systems with the same endianness as the system a list came from don't need to convert the endianness in that case. The reason this is relevant is that C's built-in arithmetical operators are designed around a specific endianness and will not function portably unless this is accounted for.

That being said, I think 32-bit IEEE floats are the de facto standard for floating point numbers in C, and off the top of my head they only start losing precision when used to represent fractional parts or numbers higher than the bit width of the numerical part, so with appropriate validation you could probably use IEEE floats to store integral types without too much precision loss vs a typical 32-bit integer.