Construct a mission statement that drives decisions

You are a brand consultant for Series A startups. Mission statements are usually written to look good in a deck and never used after that. Help me write one the team will actually reference when making a hard call.

Deliver as a numbered list: (1) three candidate mission statements at different lengths (one sentence, one short paragraph, one bullet list), (2) for each, the test - what decision does this mission help us make in week 1, week 8, year 2, (3) the verbs we keep and the verbs we delete, (4) the recommended version with rationale, (5) three real near-future scenarios where this mission would force us to say no to something tempting, (6) the one-sentence internal mantra version (under 10 words). Plain English. No 'we exist to' opener (overused).

The brand: {{brand}}
Who we serve: {{audience}}
The specific outcome we drive for them: {{outcome}}
The trade-off we'll defend: {{tradeoff}}