I am absolutely against the idea of taking a classless route.
Classes are not only integral to the games that inspire PoE, and which motivated lots of backers to support the development, but are a powerful roleplaying tool in general. Class identity means a lot more than just a pool of abilities to choose from. A Priest of Eothas is a Priest of Eothas, not some guy to which I gave a morning star proficiency and some healing abilities. The Wizard, the Monk, the Druid, the Paladin of a certain order... All this stuff is archetypical and makes the characters so much more interesting and iconic. Something that, in fact, despite all its merits, Divinity Original Sin clearly lacks. Not to mention that, even in terms of game mechanics, building around classes allows to have more cohesive sets of abilities and specializations, specific resources and mechanics, etc.
Pillars is one of the few series that still retains some sense of the fact that RPGs are not just about crunching stat numbers and telling a generic fantasy story. Keep it like that.