Here is Iowa -- home of one of the most homogenous populations in the country, we have a non-partisan redistricting process that has worked pretty well. When tidal wave elections come, as this year, this state went from being 4/5ths Republican to 3/5th Democratic. Here is more information on Iowa's redistricting process.
Frankly, if we were the old days (and to some extent the bad-old days) of districting, before it became a science mixed with voting rights laws, this election would have probably produced as many as twice the number of House seats switching hands.
Though I agree that the voting rights laws have been beneficial for jump-starting much needed African-American political representation; it also often broadly works towards a creation of too many safe seats for the extremes and a lack of broad consensus in the name of creating safe-districts which I think is now a greater danger.
I am decidedly NOT a demographer, nor an expert on the matter, but I am a believer in the system Iowa uses, while acknowledging there is a demographic fact about Iowa that makes non-partisan redistricting easier, the state is overwhelmingly white and culturally non-diverse. However, it is also very balanced between Republicans and Democrats without an extensive history of underhanded political deals and that may make a difference as well.
Would such a plan endanger the "existing" Democratic majority? Maybe a little, but I rather doubt it all things considered, as politically the Democrats have long-enjoyed generally more popular broad policies. Non-partisan redistricting is, in my opinion, the more democratic solution to the "term-limits" idea pushed by the GOP before they had a chance for perpetual rule.
But what do you people think?