I'm having trouble imagining a case where someone would point a secondary domain to the primary ibay, and not want it to behave like the primary domain. The case where you'd have the same landing page, but different sub-pages, just strikes me as foreign. I'm sure it's possible, but it just doesn't seem that likely or common. To me, it would make sense to simply change the behavior in that regard, which should be pretty simple.
However, if there are people who use it as you describe, changing the behavior breaks their setups. That means it should be configurable instead, which is probably more work than it's worth.