This is quite a simple topic that won’t take up much of your time to read.
My suggestion & recommendation is this:
Homeworld 2 races shouldn’t use the fuel system.
Homeworld 1 races should use the fuel system.
Now, before you reply in regards to balancing issues, especially that
HW2 races would have the advantage - Hear me out!
You don’t have to mirror races. This is a massive misconception
which always crops up when either developing or discussing
the development of a Real-Time-Strategy game; in whatever format
you choose, whether that be a MOBA, or 3D-Space-Combat game.
Asymmetrical races are a beautiful thing, the game “StarCraft II”
demonstrates this well, and while there are no clear counters because
of this and there are always people who complain about the new meta,
the game is still balanced and the majority of the community love it.
(And, honestly, you’re in the wrong industry if you’re trying to cater to all.)
However, this trail of thought will make balancing harder, of course - But
isn’t it worth it? To preserve the original playstyles of the races and still
along cross-timeline combat? The balance will come, maybe not at first,
but it will. And people just have to trust the developers to do that.
Lore-wise, sure, let’s say that HW1 races use the fuel system because it’s
older technology, right? Great! But how can we balance that? Given that the
weapons of the older era should also be weaker, right? Absolutely!
My suggestion to resolve this issue is to lower the cost of the HW1 races.
Make them swarm races, definitely allow the to research multiple items at
a time, and absolutely allow them to construct multiple ships at a time!
(I won’t touch on these other balance issues. Once you’ve read this thread
I’m sure you can gather what I’m getting at and won’t need that explanation.)
To summarize, my entire point is that you need to think outside-of-the-box in
a very un-original way and borrow ideas from each games for their perspective
races. If I were the developers, I’d balance everything to the HW2 races, and then
experiment with how to do the races in HW1. That is all. I hope you’ve enjoyed it!