while I like the idea [Give +1 movement to starting settler], I think I'd rather see this as a civ-specific bonus.
This is kinda Shoshone's thing that their capital always immediately has access to all nearby good tiles.
Proposal: Add "Workers, settlers, and other civilian land units gain +1 movement." to Great Expanse, the Shoshone UA.
Rationale: Shoshone cities have a habit of taking over all nearby resources, to the point where founding neighboring cities can feel wasteful of the Great Expanse bonus. Letting their settlers walk a little faster helps them utilize their UA a little better, and gives their starting settler a unique advantage when founding the capital.
Not a focus, but it also lets workers without Organization (+1 movement speed) still setup Encampments in open terrain without missing a turn of building, or camps in forests, and lets Great Persons plant their improvements with a little more freedom.
Mostly this is a fun, unique bonus to give a civ that seems to lack direction.