I think, it will be pretty inconsistent and dangerous.
First, it is not because the mage can see far, that he sees the detail where he will be landing, without additional spells. From my room, I can see the top of the mountain, which is at least a league away. It does not mean that I can see a flat, safe, unoccupied spot to move there.
So Finesse rolls are mandatory (as per rule p135). If he needs to do that 6 or 8 times, there is a fair risk of botch without Cautious with Finesse. Being relax and not threaten at the time of casting does not help with the Finesse roll, when a mage is stretching his capability that far, so it will always be a stress roll.
Remind him that if he sees only the top of the trees - England had a lot of forests at the time - the mage will be landing at the top of the trees and free falling.
You can ask him to do an Int + Area Lore to plan the most adequate "set of jumping spots", and the success or failure impact the ease factor of Finesse rolls and the number of spells required to cover the distance. Once he has done that four or five times, the Area Lore roll can be neglected, but the Finesse rolls remain.
Regarding the distance of a league, the thread you pointed gives good estimate: roughly, the distance covered in one hour by a walking man, so 4 to 5 km, about 3 miles.
To make it simple, the seven league stride would allow to cover a distance further than one can see (about 5 km at sea, without elevation, which is limited by the curvature of the earth).
This wiki page gives you the distance you can see based on your altitude: Horizon optique — Wikipédia
At 5 km, our eyes won't see any details, just some colour and contour of large items.
And to complete the discussion, using AC to perfom such jumps, require properly fixed AC. If the mage just collect some stones while walking or landing, to come back, once such stone is stored in his pocket, it will quickly loose the property of "being a stone nearby the river of XXX location" to just being "a stone in the pocket of a guy", or "a stone kept in a drawer for so many months".
So he 6 jumps are needed, 6 AC are needed, and one season & one pawn will be needed to fix properly each AC.
Teleportation is one of the most game altering effect, so discuss with your troupe how easy or difficult you want to make it:
- effect of 6 magnitude and above grants warping unless specifically designed for the target. Applied on a non-specific target - a grog for example - and with five jumps, the target has 5 warping points that bring her to the first level of Twilight with an appropriate minor flaw if non-magically aligned;
- requisits are required to carry items through TP. We ruled that anything that has 0 "Load" can be carried without additional requisit (which is usually only the clothing - no armor, and possibly a small pouch), but you can adjust that with your troupe. Especially consider the familiar case: unless a very small animal (mouse, sparrow) cannot be included in the TP without a requisit.
- it means books are bulky and requires Herbam/Animal requisit to be carried with the mage, weapons and armor Terram and Animal (metal and leather), etc...