Its not true that BeastWarriors cannot use Summon Guests, with Fairy Godmother set to heal MP, a Warrior can sustain a MP guest per turn.
A Beast build should not be using the Cha skills from Neko class, since they share the same 25% increase in skill cost of a Mage.
Beast builds are supposed to be like Mages in shifting 25% melee from their weapons combined with a 1/4 of a standard skill into a Guest, by using Cha skills over Guests, they forfeit the amount transferred from the weapon.
There is only one Summon that is worth keeping instead of a Call, which is Summon Aquella from Season of Shipping that will return next year.
If a Beastwarrior is to use simultaneously a resistance misc and Guest, it wouldn't be much of a problem to outlast a boss for an instance given a full Sp bar at the start of the battle and that the resistance misc doesn't have too much effects to increase it upkeep.
Beastwarriors have the choice of using an Elecomp skill given they have Str or a Guest, if the character has Shadowfeeder pendant for Celerity, Elecomp skills are preferred.