this type of feature of adding two boots is not in travian kingdoms; Diamonds may be used to upgrade the boots.
The theme of the travain is war
Thus like cricket and football it is not good to limit kingdom member, but limitation may be tried in the tournament
For small kingdoms they should work on diplomacy and form a bigger kingdom
Whether any limit on number of players; it does not matter. The pre-formed meta will kill the scenario. Ultimately it is the co-ordination. Thus my suggestion no limit.
All the players that settle within the kingdom should be included. We know that even the far away guys could be included.
If any limit or compromise on strategy comes; it is strongly condemned
Every players are useful for the game.
Gold players: for the game-developers and leading the team
Non-gold buyers: they provide crops as they rarely do npc; they will balance the game
Quite inactive player: useful for resources
Grey inactives: for farms
At last Both quantity and quality matter; the travian has the history of quantity wins quality,
Quality guys forget there is diplomacy for quantity
Guys, everyone has choice; it is advisable to play with own style