I agree with achow since there are some script for output and input if someone knows about your wallet and they can not access it
they can do something about requesting script or something that they can inject a code in your site or wallet that can send your bitcoin from his bitcoin address.. So i think it is not safe unless if you have a knowledge like behind the code or punnycode js or any good script just to hide access to your main account.
Vps isn't too expensive for yearly and everyone could really afford it when we talk about yearly payments it would be also a good way on storing and for Op making wallet would be possible but making a standard one isn't really appealing on the public and for sure they will use most used wallets than yours so it would be useless unless if you just use it for yourself then it would be fine.they can do something about requesting script or something that they can inject a code in your site or wallet that can send your bitcoin from his bitcoin address.. So i think it is not safe unless if you have a knowledge like behind the code or punnycode js or any good script just to hide access to your main account.
I prefer to save the wallet in a virtual machine and protect the wallet file with a zip password 
Not good idea your vps will not stay for a long time unless if you have lots of money to pay for yearly and its still needs backup your wallet.. better to use common wallet in your pc.. and make a backup in your drive D.