There is no risk of physical hardware damage by allowing someone remote access to a computer. At most, someone could corrupt the OS so bad that you'd have to reload it. But it sounds like you're prepared for that.
The absolute worst that anybody could do is crap it up with some nasty viruses. If you're going to allow the public to use it, I would physically air-gap the computer from the rest of your network so there is no possible way for a virus to infect any other system you may have. This would involve a completely independent path to your ISP. If that's not possible, then a completely isolated DMZ would be the next best option. Do not share the network this computer will be on with any other computers you have.
Also, you should be aware that there are some particularly nasty boot sector viruses that can infect the slack space on a hard drive. Such viruses do not go away simply by reinstalling the OS. You have to boot to a Linux distro and wipe the drive to get rid of those.
Along the virus thread, there are some firmware viruses out there as well. You can block these by using the Secure Boot feature of your BIOS and booting Windows in EFI mode. You will need Windows 8/Server 2012 or greater for this though. Also, some business-class computers from Dell and HP have a setting in the BIOS to require signed firmware updates which predates Secure Boot. Those can block firmware viruses even on Win7/Server 2008 and lower which do not support Secure Boot.
Other than that, no, there are no exploits out there that could destroy the computer's hardware.
they could plant un-removable malware in any firmware on the computer – Neil McGuigan – 2016-04-23T22:41:33.993