
The other route is various ways to support and encourage higher levels to do what BHM is talking about; opportunities to train, delegate, build, consolidate power/influence etc in ways that will not take away enjoyment from lowbies and if anything add to it. Elite guys shouldn't be wasting time cutting down CR1 kobolds meant for lowbies and stealing their thunder. Back in the day, it was expected that if you reached certain levels in DnD you'd obtain a stronghold and focus a certain amount of energy on consolidating followers anyway, not stomping through the Caves of Chaos monsters again.
It obviously can work the other way too as it did with Aglaril as long as the higher levels are willing and able to make it work (not always feasible) and the lowbie is willing to accept the risk/consequences of swimming with bigger fish. There's also the inherent system in DnD of lower levels in the group getting more xp which over time means they catch up in levels if they survive long enough (one of the hidden advantages of being a crafter in 3.5: fall behind in xp/level, but eventually you catch up again while getting rich - all things being equal that is).