[Railstar]

For the infected themselves, they need 2 advantages:

Reawakened = learn skills without someone to teach them.

Modular abilities = a pool of ability points that can be reallocated to different skills as the change is needed. Pick a version which can be changed quickly and without special resources, essentially "downloading" information telepathically.

Skills only (Mental skills only?) & Accessibility (only skills other hive members have) limitations could help make the price more reasonable.

Memories can be covered by skills: Area Knowledge, Current Affairs, Hobby Skill (this person), and so on.

When they need someone else's memory, assume they are using a really narrow skill (Area Knowledge: my house) at default level, with bonuses for the skill they are using being so detailed or so specific.