The problem with focusing just on the Arceans because "that is what this thread is about" is that several races suffer from the exact same problem. To "fix" just the Arceans still leaves a problem and inbalance for other races.
I agree that slow money is a problem early game for several races but that doesn't make other race's situations comparable. For example, the Iconians have access to very powerful (for early game) research modules that can get them to trade fairly quickly. That in turn can get them out of the red. The Arceans, on the other hand, do not have access to such technology The only way they can research their way out is with a little luck, like (a) an enhanced research tile on one of their few worlds; and/or (

having their survey ship find a treasure horde or two that keeps them out of debt while they research.
Further, the Arceans problems extend beyond the financial crunch in early game-that problem compounds their disadvantages later on. Their research is very slow and having only a handful of worlds only compounds that. My experience with them tells me that the Stellar Forge is insufficient to turn the tide when their enemies tech is at least one or two generations ahead and they are outproducing them. For example, in a game I played recently the Drath only had a few worlds but still were fielding fleets of five frigates with photonic torpedos compared to my small ship fleets with mass drivers. The Drath swept the field-my ships couldn't even survive long enough to penetrate their armor and do some actual hull damage.
Another thing I've noticed in all of my games with the Arceans is that coalitions tend to form against them. This may or may not be unique but I almost never experienced it playing Terrans. In my experience, it is inevitable that all or nearly all of the other races will declare war against the Arceans. This shuts down trade, a primary source of income and often cripples their economy (again) at that point.
I am currently in a game where it actually looks like the Arceans might win, but it doesn't really change my mind because (a) they have a manufacturing bonus (precursor mine) on their homeworld and a research bonus tile (precursor library) on their secondary world. Further, there were several minor races in immediately neighboring systems that were easy targets for conquest. The Drath also surrendered to me (I believe the surrender mechanic needs tweaked as races seem to surrender to easly. The Drath surrendered merely because of our relative power despite the fact that I was in no position to actually invade their worlds. Not only was my military power still insufficient, they were out of range. The AI needs to take that into account before surrendering in my opinion.)
Most importantly, I modded the stellar forge to provide bigger bonuses. Their economy still crashed but it was not as severe and because of the precursor library and a few lucky finds of treasure with my survey ship I was able to research to trade and already have a fleet of freighters deployed when the crash into red came. Of course, a coalition formed (every race but the Thalan) against me and I've been at war for the entire game with not a single period of peace with any member of the coalition. Fun game. So anyway, I still think the Arceans need a tweak or two, as I originally suggested. Whether other races need such tweaks I will leave to others.