Except that they won't. You think that there won't be multiple levels of shields and weapons? If there isn't, then what would be the point of earning money in the game, if not to upgrade your ship? And you're ignoring the point again that if the two pilot's skills are equal, the better ship will win. And having more money = better ship and weapons, and allowing people to use real cash to get that money means they'll have more money.
I think you're also overestimating how easy it will be for them to stop money laundering and other exploits. Look how long WoW has been around and how easy it is to get gold using real life cash. Game makers can never stop that sort of thing, and having it built right into the game makes it even easier to exploit.
Skill is never the same and ship modules, and ship systems do not work like levels in RPG games. They have pros and cons, they can make You faster, but weaker, or stronger and slower etc.
Your whole theory is just a theory, it wont work that way in practice. In real scenario, there is never equality, there is playtime advantage, position advantage, framerate advantage, skill advantage, module advantage, group adventage and even luck advantage.
You can easily use EVE Online as an example here, because You can buy leveled characters, ships and even officer grade modules and You still wont win if You dont know what You are doing, or You will be outsmarted by setting up good trap or someone will have good counter modules against You.
In skill based game that do not have expotencial scaling on items [exactly like EVE or Star Citizen] You cant buy power.
Buying modules or ships will only save time, nothing more, nothing less, so if You think thats unfair, go and limit playtime for players too, because those who play more also has 'unfair' advantage over You by Your definition.
If You dont like competetive aspect of sandbox MMOs, You can always play 3 different SC modes, PVE only flag for safe sectors in persistent universe, SP campaign or on MP moddable servers.