I think it's better if a player will not be allowed to attack a castle  that is low, for example castle 14 can't attack castle 1like that

New castles are usually under shield for 5 days with enough time to turn into C10. If you also are referring to the unfairness of T4 and higher castles attacking lower then why not devise a strategy to prevent this.

Traps bully the bullies! Although they take a lot of planning and it doesn't matter what lower castle you are.
Another win for the lower castles

I hope you enjoy and keep supporting Lm in its growth.

Have a nice day and message me any time

Suggestion to how to implement the Anti-Bully System:

If I am not mistaken, the solo and hell events are designed to scale in rewards and requirements using an algorithm based on castle level and total might. A similar algorithm can be set up for this system.

Instead of preventing stronger players from bullying the weaker players, there should be debuffs that come into play and it would scale using the algorithm based on a variety of variables such as total might/army strength/castle level/ anything else that would be applicable. The larger the gap between the attacker and defender, the larger the debuff.

From the 1v1 standpoint this would be effective. This can also be applied with rallies as well, factoring some similar variables and some slightly different ones as needed.

Something to keep in mind is that the debuff coming into effect would be announced/mentioned prior to the launch of the attack - a popup menu can appear with the reductions of Army HP/ATTK/DEF being reduced by x% before proceeding to the hero and troop selection screen. 

The system only applies in attacking weaker players, not vice versa.

Just my thoughts on this, there still might be some kinks to work out or features to incorporate. Overall, it would be helpful in encouraging new players and discouraging bullying.