Ah yes, it's always frustrating to find the benefits of other options after you've already made a substantial purchase.
The Bluetooth situation is... strange. Some people report good battery life with the Kobo Remote, while others report a significant increase in battery usage. The problems seem to be worse on older models like the Libra 2, so it's possible your Clara Colour would work OK, but you might end up making yet another purchase that doesn't meet your needs...