That said, it will obviously be slightly more resource intensive for those choosing to use Dandelion. You'll be maintaining two distinct mempools.
I certainly didn't think that, but since once the transaction is broadcasted to network, you simply move transaction on stempool to mempool. IMO it has bigger impact on computational resource.
I could be wrong, but since your stempool will handle other peoples' Dandelion transactions, I thought it fair to assume that both stempool and mempool would need to be maintained continuously. I doubt it will be particularly demanding on your system, though. I really like the idea.