the power lost by a clutch fan is bugger all, especially since it only engages fully at higher temps. thermo fans don't have a direct drag on the motor, but they increase the load on the alternator, which puts more load on the engine. so they aren't a free power mod as some people believe.
a big fan draws more air than a small fan as it's the tips of the fan that draw the most air as they are travelling faster than the middle of the fan (same rpm, but they travel a further distance). plenty of cars with thermo fans run 2 fans as it allows them to have different stages of cooling. for example, in some cars, in normal conditions/temps, one fan is used for engine cooling, while the other will come on when the air con is turned on.
as for looking for alternatives, sure you could look at fitting thermos, or you could just buy a new clutch for the fan.
personally, if i was going to run a thermo setup, i'd just use the factory setup off another car, and trim the shrouds as need be. i'd be looking at something off a late model falcon, magna or of a smaller fwd car such as a pulsar, corolla, etc. i'd just find something with a similar sized radiator and go from there.