Fireblade or Blackbird/R1 config pros cons ?

Right, I assume that you mean a 893 or 919 Fireblade motor. Yes, it doesn't get any more simple than this. There are more parts available off the shelf for this than anything else this side of a Hayabusa. The one thing that you haven't mentioned is weak gearboxes. By the same token the carbs aren't a major issue as far as I'm aware.

You shouldn't really include the R1 and the Blackbird in the same catagory - they may make similar power but have very different things to consider. The major consideration on the Blackbird is the need for a dry sump. They are notorious for going bang when the engine is turned the 'wrong' way without them. They are also relatively heavy but sound fabulous, even for a bike motor.

As for the R1, assuming that you rule-out the carb-fed 4XV and 5JJ which are very good motors in their own right, you then have a choice between the 2002-03 motor which was an injected version of the engine that went before it or the later engine. The later engine will just about make more power, although the difference will not be as great as the manufacturer's figures suggest - in a car the later engine does not benefit from the ram-air effect as it does on the bike. The later engines also require some mods to sort out the breathing which can be very heavy.

To answer this much more fully would take an age because you there's a lot to consider even before you open-up the discussion to the CBR1000R Fireblade (race proven but VERY tall) and other alternatives like the ZX-10R (Fab but requires high final drive) and ZX-12R (possibly the best bargain of the lot.)

ETA: this is bound to have been covered-off on here previously, and if it hasn't, get yourself to www.locostbuilders.co.uk where it certainly has.

A good Megablade would be several seconds a lap quicker around a track that a 150bhp S1 Elise. Slightly less power and torque massivley offset by about 300kg weight saving just for starters. My old 893 blade was indestructible, but a bit long in the tooth now and hard to obtain. I think simplicity now starts with an R1 which just needs a modified sump to run reliably.