@huanghq
thanks a lot for creating this walk-through it was so useful
I do not think that USB stick is safe wallet - there can be a lot of problems. For example, there are viruses, that use USB stick. And if you use one Linux OS - you can use only that one Linux OS, so you can not use USB stick in other machines with different OS then.
i have never head of virus on linux! there is none.
the only risks for using this way are: forgetting your passwords and damaging USB stick physically nothing else comes to my mind
and for preventing these two you can write your seed and/or passwords on a piece of paper and keep it safe