On the other hand, value semantics are just plain easier to reason about.

My 2 is your 2. We don't have different 2s because it makes no sense.

But sometimes you don't just want a 2, you want a pair (2,3). All of a sudden, my (2,3) isn't your (2,3), unless you call equals instead of ==, and remember to implement equals() (and that demands implementing .hashcode() too, and probably a toString() while you're at it). While it's easy to forget about if you've been using Java for a while, 2 gets passed by value, but your pair gets passed by pointer-value.

So I'd come at it from the other side. Pick a value representation of (2,3), reap the simplicity, and hope the sufficiently smart compiler is smart enough to do good things with it.