I just tried, the kph40i drivers are easy to pop off (I'm honestly amazed they haven't broken with how roughly I treat them) and I couldn't dislodge the 30 drivers from the headband. I'd say no, also the 30's headband is not fragile say you'd have better luck with the 40s, the 40's pivoting driver is kind of flimsy feeling and just rattling around my bag has popped the driver off multiple times (never broken but still, I don't just toss them in my bag anymore)

The 40s do sound noticeably better than the 30s to me, though. I threw some yaxxi porta pro pads on them and they're fantastic

If you love the koss on ear stye, I think they're a proper improvement over the 30's. But if what you're after is more durability, I think the issue is a wash, I'd go with some regular grado sr60's for the on ear hifi, and you can actually replace their headband with a more durable one from aliexpress if it ever breaks.