Basically, can you explain the rules in a more accessible way that doesn't require prior knowledge of other games? Unless the pitch is literally "a forum game version of Rule the Waves" and you intend for only people familiar with Rule the Waves to play, in which case do what you like
The idea is for a navy simulation game. You get to control a navy or maybe a shipyard or shipping line in the rapidly changing world of the early 1900s. There would be some systems for prestige, power, and tension (they would help determine the budgets), and probably commentary on the naval arms race and completion between various ocean liners. High tensions help boost the naval budget, but they also increase the risk of war. Some of the dynamics with prestige and power are probably similar to Balance of Power
(which I've never actually played), but I don't really intend for those points to be used to determine a winner at the end of a round. Players can decide for themselves how they've done, and it makes it more fun to be a smaller power too.
As time goes on larger ships with better technologies can be built. Both military ships and passenger lines keep getting better every year. Ships are moving from coal fired reciprocating steam engines to petroleum fired steam turbines, and warships keep getting larger guns in increasingly more sophisticated turrets. Given the rapid pace of technological advancement in the early 1900s ships might be obsolete the moment they are commissioned for service only a few years after being laid down.
The biggest thing to decide on is how combat, races, and other competition would be resolved. Some navy forum games take more of a roleplaying approach and just have people work out simulation happens among themselves. Other approaches would involve various degrees of simulating. There's room for both approaches of course (roughly approximating an outcome and then filling it with details).