3 methods of opening the lock, You have quite a good idea to buy such a lock is likely to be a problem, the easiest way to open the door is push-button pin code - it needs to be long enough that it would be quickly picked up, on the one hand you can buy the most suitable lock and modify until like that. The question of power is considered not so important if you duplicate the system, the battery - lock you can still open the key. About the programmer, I would say that you need it - useful in General from time to time to change passwords (and if card lost), if You go to reprogram (reflash) the card to someone else it is a duplicate and can remain there a security issue comes out!
Now here is an interesting article with links about smart locks and reasoning about security https://geektimes.ru/post/291949/
(by the way I support the author on the insecurity of the castle with Internet access)