Forwarn would help this pokemon tell opponents best moves. This could help with Salamence (e.g. Draco meteor or outrage.) In the long run, it might be better than Frisk.
EDIT:Although, now that I think about it, Arena Trap would help scoutmon scout. Why? Because arena trap is almost always a good ability. Proof is that Dugtrio is in ou, when it only has a bst less than ponyta.
Arena Trap would NOT help scout, as scouting requires that your opponent be able to reveal more of their team. They can't do that if they're trapped, can they?
Obvious abilities are anything that reveals information about the opposing team (Forewarn/Frisk, Download/Offensive Download), provides an incentive to switch out (Intimidate mainly), or provides an immunity (Immunity/Insomnia/Limber/Quick Feet (better than limber, since it turns Paralysis into a status block and speed boost, while simultaneously providing some bonus from other status effects), Flash Fire/Motor Drive/Water Absorb/Volt Absorb/Levitate, Natural Cure to another extent).
Another ability that bears merit would be something like this: When this Pokemon Switches in, automatic Taunt on the Defending Pokemon.
An alternative to that would be this: This Pokemon is immune to the effect of non-damaging attacks from the opposing Pokemon.
The second version protects ScoutMon even if they switch out, but cannot stop stat-uppers, and does not have a duration that wears off (if it were programmed exactly like Taunt, where it has a 3-5 turn duration).
The first version provides the ability to scare off walls, as being stuck in without the ability to recover or status hampers many of them. The second version works as a catch-all protection against Status effects (except as secondaries, from things like Thunder/Discharge), but still allows healing and entry hazards to be set up. The first also bears mention as a catch-all way to prevent Leads from setting up Stealth Rock.