Hm... if anything, I would place scouting under normal warriorhood, instead of an alternate rank.
There wouldn't be any real need for a distinct suffix. A -nose cat, for example, may be a good scouter because they notice everything, and would be able to smell out the best places to rest. A -claw cat might be a good scouter because they're capable of handling themselves if they go ahead alone. A -foot cat would be a good scout simply because they're quick enough to run pretty far ahead, gather all the information they need, and sprint back home to report. Any cat could be a good scouter because their particular traits help them to keep an eye on things ahead.
Now, let's say they were heralded as just as important as, say, a medicine cat. We've seen before that a Clan without a medicine cat is a Clan in very, very deep trouble - a nomadic Clan especially so! There's no one nearby that has a high likelihood of knowing every single herb in the country, so if they lose their medicine cat, they're boned.
A scout, on the other hand, is someone anyone could be. Really, I'd say that a nomadic Clan would change around their scouts regularly to keep just one cat from expelling all their energy. On the other hand, if the cat's job is to scout out multiple trails, decide on the best one, and then report back, then it may be considered a special rank since that would require a lot of intelligence, endurance, and observation skills, on top of being a fast cat to report back quickly.
If that's the case, then we should be looking at what an average scouting cat would look like. My guess is that they would be a fairly lean sort, with a lot of muscle in their legs and sharp senses. They would be known for a sharp eye and quick deduction skills, even at a young age, and they may switch from being a warrior's apprentice to a scouter's apprentice, or even just become a scouter as a warrior, since that sort of ability takes time to master and the Clan can go without a specific scout for at most a week.
And if there is indeed a specific scout rank, then what would a scout be best known for? A fast cat uses their feet, a strong cat uses their claws, a hunter uses their whiskers, and a climber uses their tail. Swimmers use streams, medicine cats use leaves, etc. Remember that we're not talking about a specific personality here, where the suffixes become metaphorical (-heart, -storm, -cloud), but an actual skill, where the name is literal (-claw, -nose, -leaf).
So, as my final conclusion, I would suggest that a recognized and ranked scout cat would be given -eye if they are particularly skilled at their job.