E-VOLUTION IS A MISTER E

>building a fanless desktop computer as a NAS
Feasible or ridiculous?

Context
>want NAS
>for various things but nothing heavy, probably idle 99% of the time
>array is currently made up of 4x 2TB 2.5" disks
>use old laptop, mix of internal bays and USB
>so far so good
>but fan is always going no matter what
>old Sandy bridge CPU, doesn't have modern efficiency features so fan is going at a certain base level all the time no matter what (yes thermal paste is good and recently refreshed, and fan/heatsink part is new too)
>don't want fan going 24/7. (a) it's not needed, idle 99% of time. (b) unnecessary 24/7 of moving part which isn't designed to be used 24/7. theoretical fire risk. (c) surprisingly annoying noise
>unplug fan from motherboard
>it works, temps barely any higher
>but boot problems. comes up with "Fan error" and won't boot
>only way around is to physically be at computer on boot/reboot and press Esc immediately
>it's a NAS and disconnected from outside net so it will hardly ever be rebooted, but still, annoying that reboots can't be done from afar, whether across local network or from outside of network
>look at chink fanless mini PCs with maximum USB ports as an alternative
>theyre not actually as cheap as i expected for what you get, esp those with ancient CPUs. kinda feel like a scam. also they are focused on lots of ethernet ports and com ports which are irrelevant to me. And they don't seem to have TPM modules - i like to encrypt all OSs.
>so, crazy thought...get around all these restrictions by building my own fanless NAS PC

How crazy is this idea?
Either a big giant desktop type where all the disks will be in the case (current array is 4 disks, but i want expansion room to at least 8 disks)
Or something smaller, something mini but ensuring adequate USB ports/bandwidth in order to attach all disks by USB