I've not delved into the more exotic coins in terms of purchase but looking at doing so now.  I've used a hardware wallet up until now but this won't support the lesser known coins. 

I don't want to buy a separate laptop to use for that purpose.  Can I use a bootable usb drive?  Presumably whatever happens within that "OS" has nothing to do with anything compromising that could potentially be on my main laptop OS?

Can I store keys on that drive and make copies of the complete drive?

Presumably, I'd have to go online momentarily whilst using that flash drive to transact into or out of it.  Even if for a couple of minutes, is this an issue?

What other considerations are there for a bootable flash drive crypto solution?