I worked with bitcoin before and there is some fee per transaction byte is used. Depending on that I can control the expected confirmation time. But here I do not see any similar logic.. it looks like I should use some universal gas price, correct?
So it turns out Unity can interface with native and managed (.NET) C++ DLLs so all I need to do is package Solidity into DLLs for import into Unity, I hope fingers crossed otherwise I'll figure out a way to convert to C# or write a C# wrapper for Solidity cpp.
If it works I'll provide the Unity DLLs for Solidity for anyone else who needs to use the compiler.