I'm looking at a fairly feat intensive build making use of rogue talents and something that occurred to me was perhaps being able to "shuffle" my feats and talents to get better use out of them. Admittedly I might end up just wasting gold but here's a full explanation:
Basically using the Archaeologist bard archetype to build a whip focused character. Whip Mastery requires +2 and Weapon Focus, Focus requires +1 and I don't start with +1. So basic plan was simply retrain lvl 1 feat at lvl 2 so I have all the requirements for Whip Mastery at lvl 3. However at lvl 4 I finally get a Rogue Talent.
Now while Combat Trick would work fine here, it might be more useful for something else down the road (as my understanding is you can only take it once). My thought was to retrain my Weapon Focus into something new, and take the Weapon Training talent instead. However I could see some potential issues.
An alternative, if more expensive method would be retraining both Weapon Focus and Whip Mastery, taking the Weapon Training talent then retraining the feats back in. I don't think I'd be running into issues with legality. The downside being it's four times as expensive.
The gold costs don't amount to much, in the grand scheme of things. Are you going for weapon finesse with that? You could probably squeeze out another feat from the talents if you are, and don't go for unchained rogue for some reason.
If you're playing PFS, the prestige cost is rather hefty. Otherwise, it's legal.