I've copied this from a post I put in the Lombard RAC Rally thread in leasure lounge.
"The problem with superchargers is they actually consume power as well as creating it, so there comes a point where they become inefficient, but they have no lag being belt driven, and you can't just wind up the boost like a turbo because it is constrained by the speed the belts turns. Thats why you find superchargers don't get used that often. OK the MINI Cooper S has one, which shows what can be done with an old Chrysler engine, tis true the MINI engine is same as the Neon that thoroughbred of a car, but the rumour is that the MK2 will be turbo charged with a better BMW designed engine.
Turbos don't consume any power at all being driven by the exhaust gasses, therefore the are more efficient and can spool up to any speed creating almost endless amounts of power, but of course you have lag as the exhaust gases build up, the bigger the turbo the bigger the lag, but engines and turbo's are getting better all the time & the noticeable lag in some modern turbos is negligible, SAAB, Volvo the VW/Audi group all do low boost non-lag turbo engines now.
Lancia tried to overcome this with the Delta S4 which had both, a small supercharger to gain lots of low down torque & over come the lag & a big turbo to kick in when the supercharger wained, it worked as it produced over 600bhp from 1.8L."
NEW BIT WHICH RELATES TO THIS THREAD.
To be honest there is a negligible diff in reliability of a super charger versus a turbo charger as both spin at very high speeds, at very hot temperatures & need a good supply of oil to feed them, there are many a SAAB (US market their biggest) 900 Turbo's out there with way over 200,000miles on them on original turbos. Remember in the US an engine has to pass a reliability test where you have to bench test the engine to cover 110,000miles without changing anything except maybe oil?, (as an aside, this is why Lotus moved to the Toyota engine in new Elise as the engine had already got US approval)
As with any boosted car that was not intended, it all comes down to quality of job, and consequent servicing by the owner as you will need to increase service intervals for the consumables like oil, filter etc. but any boost job will show up if they drive train or cooling system has any weaknesses.
On a small engine like the Cinq a super charger has its merits, but the extra space needed to get a belt drive could prove problematic.
If someone thinks they could do it, & you had the time & money needed to do the job, I would say go for it!