Well I have to respectfully disagree. Particularly when the perception is that this particular "upgrade" is described as "butchering".
"Devaluing" is a relative term, in that it can be temporary or permanent. In this case, this is no more devaluing than plugging in an external hard drive into a serial port. The ROMs are socketed, so they easily pull out, the board goes in, the ROMs go in, the cable comes out through the battery access, clean and elegant. The Mac is still original but can now be used with a modern storage solution. All one has to do to return it to stock condition is unplug the board and re-seat the ROMs, in principle no different than unplugging an external drive. No damage is done to the existing case or hardware. If I saw such a unit on eBay with the board installed I would still pay top dollar knowing it could easily be restored to stock condition, especially if the 64K ROMs were still intact as with this process.
As for the original philosophy, even the external floppy disk drive goes against the grain as anything the customer ever needed was already built into the box, including all the storage they ever needed (the ext. FDD wasn't even available until 6 months later). Perhaps it goes against "Jobs' philosophy" but in agreeing to allow the ROMs to be socketed, he unwittingly agreed to the addition of another port. Also, had SCSI existed as a universal standard in 1983, it's arguable whether it would have been included on the original Mac. And if USB had existed we would not be having this argument. Jobs had no qualms with expansion, he simply wanted the Mac to be a closed box with the user only able to add onto it via the ports and software. The fact one has to open the box to access the ROM sockets is a trivial technicality. I see this no differently than the commercially available Quark QC-10 hard drive which also connected to the floppy disk port against Apple's guidelines, yet the use of which did not void any warranties.
As for voiding the warranty, even at the time that is highly unlikely since the board can be easily removed with no traces it was ever there, hence the devaluing argument. Jobs might have even applauded this solution as he later did the engineer's RAM expansion deception which saved his ass, since it plays by all the rules: it uses an existing "port" interface and is essentially a software solution. In fact, if I had to sum up Jobs' philosophy of the original Mac it was: the customer should pay for a new model if they want new features. Almost no one at Apple felt that way. So it's a question of whose philosophy you apply, and I would argue we are long past being concerned with the philosophical motives behind the original January 24th introduction. For the advantages offered by the SCSI board adapter, this particular argument is moot, especially considering the alternatives to hard to find and failing parts every passing year virtually ensure usually destructive upgrading it to keep it useable.
Either way, "butchering" is the last word that should ever be used for a non-destructive modification, especially this one.