Há uma FAQ relacionada a isso:

Summoner: If I choose the reach evolution for my eidolon, how many of its attacks gains increased reach?

The ability description says "pick one attack," not "pick one attack type." So if your eidolon has two claws and you pick "claw" for the reach evolution, only one claw gets increased reach. (The reach evolution is intended to let you emulate having a dragon-eidolon, as a dragon's bite attack has greater reach than its claws.)

Se nós extrapolarmos isso, se você tiver 4 armas fabricadas, apenas uma dessas armas fabricadas ganharia o alcance, mesmo que sejam todas da mesma arma

Nota: Esta FAQ é para o evocador encadeado, embora eu sinta que ainda é relevante desencadear também, considerando que a evolução Alcance para ambos encadeados e desencadeados está expressa exatamente o mesmo. Assim, na ausência de qualquer texto específico em outro lugar para o eidolon desencadeado, eu diria que a intenção é a mesma, e esta FAQ se aplica.

Apenas percebi isso enquanto observava as possibilidades e senti que valeria a pena ressaltar.

Dando ao seu eidolon um aumento de tamanho, você terá alcance para TODOS os ataques!

Large (Ex)

Source: PRG:APG

An eidolon grows in size, becoming Large. The eidolon gains a +8 bonus to Strength, a +4 bonus to Constitution, and a +2 bonus to its natural armor. It takes a –2 penalty to its Dexterity. This size change also gives the creature a –1 size penalty to its AC and on attack rolls, a +1 bonus to its CMB and CMD, a –2 penalty on Fly skill checks, and a –4 penalty on Stealth skill checks. If the eidolon has the biped base form, it also gains 10-foot reach. Any reach evolutions the eidolon possesses are added to this total. The eidolon must be Medium to take this evolution. The summoner must be at least 8th level before selecting this evolution.

If 6 additional evolution points are spent, the eidolon instead becomes Huge. The eidolon gains a +16 bonus to Strength, a +8 bonus to Constitution, and a +5 bonus to its natural armor. It takes a –4 penalty to its Dexterity. This size change also give the creature a –2 size penalty to its AC and attack rolls, a +2 bonus to its CMB and CMD, 10-foot reach, a –4 penalty on Fly skill checks, and a –8 penalty on Stealth skill checks. If the eidolon has the biped base form, its reach increases to 15 feet (10 feet for all other base forms). Any reach evolutions the eidolon possesses are added to this total. These bonuses and penalties replace, and do not stack with, those gained from becoming Large. The summoner must be at least 13th level before selecting this option.

Embora o alcance não garanta a concessão de todos os seus ataques, você pode tornar seu eidolon maior ou maior para alcançar 10-15 pés de alcance!