I'm very similar to you by the sounds of it Neil! ;)
My intention with buying the ISF, was to get something that was a lot newer than the Supra, that didn't need much doing to it. Afterall, this is a genuine super car right out of the box.
Thing is I'm a fiddler when it comes to my cars. Like you, even if I bought a Lamborghini, or an Aston Martin, I'd still find ways to tinker with it! ;)
Hardly any car is setup to be bespoke to a specific driver. My needs wouldn't have been considered by Lexus when they developed these awesome cars. If they had, the centre console and switch surrounds would have been genuine carbon fibre for a start! ;)
My point is a manufacturer develops a base for as broad a market as possible. The bigger the target audience, the more units they sell. Whilst Lexus are renowned for many great qualities, building performance cars isn't one of them. The fact the ISF was dreamed up by some technicians over in Japan, that had more octane in their veins than the rest, says it all.
500HP should be the figure from these cars in my view. Not 499, or 417, but that magic number, 500.
They also kept it refined to try keeping some of their LS and GS buyers interested I imagine. Remember my Dad getting his LS400 back in 1994. It was super quiet inside (you couldn't hear the engine on tick over at all!). Loved the ride as a passenger, but it was lacking in feel or excitement as a drivers car.
The ISF is a great car without question, but with a few changes here and there, it can be an amazing car.
:)