With how the clan combat xp event is set up, it highly supports having alts join to boost the xp that main/higher levels can receive while reducing the amount of xp lower levels can receive, thus discouraging lower levels from participating with the clan. This seems counter productive to a clan event.
With the loot event, having alts join grants a higher percentage that a player can earn loot rolls, which in turn reduces the chances for rolls for solo account players.
And then there is the whole bit where players have alts that exist to farm up materials to support main accounts which feels like an unfair boost, making it feel like players need alts in order to keep up with other players with alts.
My recommendation is to allow alts of different categories (normal/ironman) but to disallow creation of multiple alts for the sake of boosting a main account.

