For a brown ale I think 1.4lbs of caramel malts isn't that bad unless you are going for the hoppier end of the style (I'd almost bet most of the issues that stem from a beer becoming too sweet and high caramel malt bills are from fermentation issues rather than recipe issues).
The flaked oats and barley probably will have the least amount of character but will add body and such to your beer. The wheat and rye will add some of their unique character to the beer that may come through in the flavor. If you are a fearless person though the flaked rye, lightly toasted in the oven, will in my experience add a big creamy almost oily character if you don't do a beta-glucan rest, its fun to pour a cold glass of a beer with lots of flaked rye in it, looks like you are pouring maple syrup. Though it will add that rye spiciness, but if you are gonna age it on oak with whiskey it will probably actually compliment the beer.