With the smaller Lindbergs there is the possibility of just butchering a (standard size) servo for its motor and electronic board, fully proportional forward and reverse, a lack of deadband, but do you sail your boat to look at it sitting there? Limitations are that power is the RX battery, usually 6v max. If running Lithium, a voltage regulator might be needed for the electronics, a voltage warning circuit will almost certainly be needed. The required extra electronics will eat into the weight advantage of Lithium, against the basic simplicity of NiMH.
Also - http://www.mr-rcworld.co.uk/index.php?productID=1010
Small, full function. Relay reverse, 2A, up to 30 volts (so the maker tells me)
The Chinese 10A ESC is good for up to 8.4 volts and has its own BEC. Its off position is heavily offset (probably designed by a Futaba user), the deadband is wider than normal, and seems to give more power in reverse.
If doing one with more than one motor, I would opt for a pair of these - http://www.action-electronics.co.uk/speed.php
with one of the same company's mixers. They are a class act and simply work out of the box, but are strictly limited to a regulated 5 volts, or 4 NiMH cells. Works great in my minesweeper off 4 AA.