"if there are no aliens, infinite wealth is ours for the taking, and the expense associated with a fleet is meaningless. if there are aliens, the fleet is an utter requirement".
to build a fleet is literally the dominant strategy.
That is like you saying you are going to spend the majority of your life working for no gain in the notion that there "might" be some imaginary event instead of spending your life doing something really worth while. You can still save some resources as an insurance for a rainy day but you are not going to spend the majority of your energy for nothing if you are able to do otherwise, that would be a sad life spent. Time is a very real resource for "real" people who actually do inhabit your "game"...
There would be no reason for us to prepare for some imaginary hostile intelligent life from a realistic perspective without some evidence for it. Just because we figure out a way to travel the stars does not make intelligent life more likely out there, I would say it would make it way less likely if there was an easy way to travel the stars from a logical perspective.
Now... you can easily have a role-play story about an alien artifact that was found on Mars that contained the knowledge of untapping the power of trans Newtonian materials and that this artifact only was perhaps 10-100.000 years or so old. Then I might see a reason for investing in some military preparations... although if you met that alien I don't think it would matter anyway...
...and they have already been here and left this artifact in the hopes we one day would find it... what are the odds they are hostile to begin with?!?
I think that for most people playing it has more to do what is cool rather than being realistic... because it is fun... and there is nothing wrong with that. Some people do it because they know for a fact there is aliens out there as they played the game before (or simply know), so it is less about role-play and that is fine too... nothing wrong with that. It also is perfectly easy to make up a story, you can rip it right out of the "Independence Day" movies if you wish. I think that rationalizing building a large military fleet before evidence of an advanced hostile alien intelligent life are generally weak backtracking logic, but that is my personal opinion... you can do much better if that is your intentions. I bet there are many good stories playing out in peoples heads for why they do the things they do. Some people play it as a pure game, some play out a specific story in a specific setting and other go all in on role play and try to rationalize every decisions made as if it was living breathing agents with real unique motivation and allow the game to evolve naturally from there without a specific end goal of the setting in mind. Aurora inspires role-play in a rather diverse form so there is no wrong way to approach it.
So my objection is not one of the direct technical nature but one of logical economic and development level. A focus on an efficient defensive strategy together with an aggressive expansion philosophy would make you even stronger the day you "actually" meet that potential enemy we all know you will eventually meet. Investing in an expensive military will hugely hamper you economic and scientific progress for no real gain as that fleet will be outdated much faster than an otherwise leaner military can be updated with better technology and more focused on the task at hand. In my opinion it is a win win scenario all around.
Investing no resource what so ever in a military is from a role-play perspective quite a sane strategy if we have no evidence for intelligent life, it also pose a pretty interesting challenge down the road.
In my opinion the proposed carrier fleet doctrine are quite sound in theory and very fun to pursue and I see no direct problem going down that road. As long as the player don't explore the chances to meet any aliens are pretty slim. If you did not create any starting aliens either the chances are zero and you literally have almost unlimited time to build up (depending on resources in Sol that is). I know allot of people who mention they expand very slowly for the fact they are less likely to create aliens that way and stay in Sol for the same reason for a long time.
Personally, if I play a standard Earth unified start with no knowledge of any aliens, I just expand like crazy as that is what I believe we would do if we could. It obviously almost always end in some sort of disaster but that is the fun part.
