I agree that they never could have developed those 'local' races to the same point as AQ races or some of the GQ races in DS9, if they were to hold to their premise of trying to reach home and actually getting closer to home over the series' run. I also agree that the Borg could always be there, but that they were so overpowered they couldn't show up too often without it looking highly improbable that Voyager kept defying the odds.
There was another narrative structural element thought that they could have used as a theme throughout the series, but that they ditched very quickly. I'm talking about the internal tensions in the crew. Initially this was along the fault lines of Starfleet and Maquis. Though I think that holding on to that specific division in itself would not make sense (the Maquis after all were only disgruntled Federation (ex-)citizens and they had no cause to keep the conflict with Starfleet up, at least not while they were in the DQ), I could have seen the division line develop more along those that wanted to adhere to Starfleet principles - no interference with societies not ready for it, no affecting local balances of power, etc, and those wishing to manipulate local circumstances to their own advantage ('so what if we give replicator technology to species X if they tell us where that stable wormhole is?'). We might have gotten story arcs about a crew that is mostly dependable but sometimes a part will act behind Janeway's back, and her command is never quite strong enough to fully flush them out and yet she can't run the ship without them, so she has to compromise a bit between 'Starfleet Principles' and simply getting her ship home. A bit like how Sisko could sometimes be at odds between his Emissary and Starfleet duties.
Instead, what we got was that beyond the first half of S1 perhaps, it was simplified to the Unquestioningly Loyals (nearly everybody) and a very few Traitors - and even that only lasted till the death of Seska, end of season 3.