No, if you attack someone for no legal reason, you lose your ship, you lose security status and you have a kill right on your head.
Enforcement of the consequence of that gank is an issue (or not, depending on who you ask 
) but there noticeable consequences for your illegal action. With your system, you can just bounty some people and get them killed legally without consequences for you. You can do that from an NPC corp, you can do that from a hollow player corp as well. It does not matter.
You can even counter bounty them but considering that the majority of the bounty hunters will be alts of bounty hunters, you have again created a way to exploit the system to collect bounty put on your head instead of being a punishment that you envision.
No, if you declare war on someone, they can fight back properly, they can invite allies to fight you in their place or with them, they can attack your assets, they can also counter wardec your neutral assets if they fight out what your neutral holdings are.
If you wanted to do that, why didn’t you check out the other topics that wanted to flesh out a new bounty system and offered exactly the same flawed system. Here is a list. This suggestion even has the same NPC mission involvement as you suggest.
In short: All bounty rework ideas always bounce back to my 3 points above and all so far conceived suggestion were abusable without a positive effect in return. If you want to flesh out something new, try to figure out a way to prevent this abuse without limiting the bounty system too much. For instance, some people suggested you should only be able to bounty someone if they illegally harm you, declare war against you or went suspect on you for some reason but what about the remaining 95% of the players that you could not bounty. For example, currently someone can place a bounty on me for criticizing your idea. Other people already bountied me for talking in lokal, mocking them or because they were competing for asteroids or missions in a system. That would not be possible under a system with strict limitations. If you can figure out a way to allow bountying for both scenario scopes but prevent abuse of mass-bountying or killrights for ISK, you would have solved and age old problem in EVE and would be a hero. So far, however, your suggestion is not better than any other in the list I linked.
I may come across as argumentative to you, but I am just sick of the ever same suggestions to cater easy kills to cowards in high sec so that they do not need to risk their own assets.