You're glossing over my question. If Germany was more heterogeneous, with more political conflict between groups, would folks in Germany be trying such measures?
Half of Germany was a communist country until 30 years ago while the other half was a wealthy democracy. Not sure how much more heterogenous than that you get, politics-wise. There remain fairly dramatic political differences between the former east and west.
My second hand understanding, though, is that west Germans consider East Germans to be the same people and the integration was viewed as a reunification. Not quite the same as different groups who perceive themselves as distinct and with conflicting interests.
Generally, in a democracy, more voting is, at least publicly, considered better (in private, of course, some party officials might disagree, but the backlash if they tried to _do_ anything about it would be unthinkable).
I actually wonder to what extent this is a function of how democracy developed in the US vs everywhere. At least in the popular mythology, voting went from available to all male members of the ethnic majority, to all members of the ethnic majority, to everyone (this isn't actually quite true; a number of southern states had property qualifications for whites pre-civil war). Whereas a more common pattern of development elsewhere was the vote for practically no-one -> the vote for a very few (property qualifications) -> the vote for all men -> the vote for everyone. Most people in Europe will need to look back no more than a few generations to see where _their_ family wasn't able to vote, which may cause people to be more defensive of the institution.
There's also the example of history; most of Europe's 20th century totalitarian regimes screwed with voting early in their development.