Fudge is there to be hacked and I don't think switching from Fudge dice to 3d6 is itself a bridge too far. The roll under however does create a complication in terms of accounting for Difficulty Levels.

Fudge works the notion that Ladder covers both the character's skills and the relative difficulty of the task, the Difficulty Level. The ancient scroll poses a GREAT  challenge to translate. If my character's Ancient Languges skill is GOOD, he's chances of success are slim.

How would that work with a roll-under skill approach? Would roll GOOD or less be treated as a success or would you need to add modifiers to the dice roll to reflect the higher difficulty the scroll translation requires?

Polar Blues wrote:

The roll under however does create a complication in terms of accounting for Difficulty Levels.

That seems like the key obstacle to me as well. A system where you have two versions of the ladder, one of them effectively reversed for difficulty levels, is possibly a solution but awfully inelegant and seems like an added complication. There's probably a better way to handle it.

It rather reminds me of the issues that Silver Age Sentinels had: it took the d6 roll under mechanic of Big Eyes Small Mouth and applied it to superheroes, with stronger characters timing bigger dice… which meant that the better you were, the harder it was to succeed. Recognising that, the designers pretty much added a fudge to the rules, resulting in a workable but clunky version of a previously fairly smooth system. The tricky part with making a 3d6 Fudge is going to be avoiding losing the benefits of both 3d6 and Fudge by creating a less usable hybrid.