[dreamfactory]

Depends whether your milestones are measured in time, features, business outcomes. First would still be t&m - just be a larger unit than days; second would be classic fixed price billing (which incentivises low quality hackily bolted together solutions which will be a pain to maintain and extend); third would be value-based consultancy.

[lifeisstillgood]

This is a fair insight - there are always milestones - the ones you agree to get paid by affect the project as a whole

I would suggest talking in terms of features / business outcomes.