Personally, I'd drop the Ranger and pick up a Druid, but I have a real weakness for Bards. That being said, if you want to drop the Bard and replace it with a Druid, you won't be really missing out on much. You'll gain a secondary healer who can act as a secondary tank as well, and you'll lose the Bard's Lore (replaceable by the Identify spell via your mage) as well as arcane spells, but you'll gain some of the awesome Druid spells. Not a bad deal.

If you keep the Bard, be aware that Bards cannot dual class. Like the Paladin, they're stuck as a single class only and cannot be combined with other classes either via dual or multi-classing.

Oh, and you don't need to use an editor to replace the Bard. When you start your game, you can delete the Bard on the screen that shows your party members (just prior to the game firing up) and just roll a Druid. Just be sure to strip the Bard of all his gear when you save the game prior to doing this.

*edit* One more thing: I'd recommend exporting your Bard before doing this, just in case you decide you want him back after trying out the Druid.