There's Dropbox paper and Google docs. Both are more searchable than confluence.
From my experience of Google Docs I think you'd be trading problems.
Never used Dropbox Paper though. Biggest problem is that outside tools will always be a hard sell, living in Atlassian world (Bitbucket + JIRA + Confluence) it's really hard to convince business to pay more for an extra tool, when they're usually fine with Confluence, or at least I get the sense that tech people are the ones who struggle most with it.
Maybe adding cookies to the proposal would do the trick! :P
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