As title says: Since I'm multiclassing into both Rogue and Scout, I have the Trapfinding ability granted to me from two different classes, and as far as I know they don't stack or improve upon each other at all.
Currently what I know of are three ACF's for the Rogue that would work.
Antiquarian (CC, p 51): lose trapfinding, gain wisdom bonus on appraise checks with divine items. Can attempt to identify divine items, as per the spell.
Drow Rogue (DU, p 58): lose trapfinding, gain poison use.
Mimic (EoE, p 21): lose trapfinding, gain disguise self.
Is there anything else out there that I can work with? With the build I'm going for the Drow Rogue looks the most viable but really poison use appears to be more trouble than it's worth (especially with the cost of decent poisons...)
Basic level progression is Rogue1/Scout3/Ranger1/Scout1/RogueX, I'm starting the campaign at lv6. (Would be lv7 but I'm using a Dark (LA+1) Lesser Tiefling, and LA buyoff is allowed). Feats by lv6 are: True Believer (1); Point-Blank Shot (1); Darkstalker (1); Deadly Aim (3); Swift Hunter (6); Swift Ambusher (6). This is to get me able to get both Swift Hunter and Swift Ambusher by level 6, and progress in Rogue after. So, I get Favored Enemy: Undead, Skirmish, and Sneak Attack. (all levels stack for Skirmish, and I can Skirmish undead)
Among my gear are various means to stay out of direct light as much as possible to use HiPS from the Dark template, as well as a Raptor arrow and a bow enchanted with an infinite On Use Sniper's Shot spell effect. Feats on my list to get ASAP are Vital Strike and Improved Skirmish, and gear to get later include Gloves of Agile Striking (improved), Skirmisher's Boots (improved), and Rogue's Vest.
This build is aimed at shooting one arrow per round, and having that arrow bring as much pain as I can stack onto it.
We do not play a high optimization game in our group, so I'm happy with this build in general even though it is not optimal.