I know your question was about styling it, but I just can't help it: I love looking for info on species. Well, this is part of the pleasures of bonsai, isn't it?
So, just skip this message if you don't bother too much about this, but I think your coto might be a
cotoneaster bullatus.
I first had a look at "Shrubs" by Roger Pillips and Martyn Rix (Pan books, 1989, a must, I'm sure it has been reprinted, it's so good), then i cross-checked on Google.
Here is what I found :
" A robust shrub with soft bronze juvenile leaves, small greenish-pink flowers, and red berries." The photo on the same page looks a lot like your tree :
http://www.howhill.com/potluck/plants/shrubs.html
Well, if it isn't, at least I've learned something, I didn't know that one.
Best of luck with your tree.
A.