>>10895346>I've heard that resin kits can be pretty brittleYes, but not nearly as brittle as UV resin 3D printers use. It will crack if you try to stuff a peg into a hole that is too small or if you try to cut a piece off with dull nippers or something, but it won't shatter into a million pieces when dropped.
>I'm wary of sawing off huge chunksYou can saw regular resin just fine as long as your saw is sharp and you are actually sawing rather than trying to break off a piece.
>or trying to hollow any parts out too muchAnything will lose structural integrity if you hollow it out too much.
I personally would probably go with your first approach as long as you're sure the plastic parts' dimensions are compatible with the resin part (but if they're not you can just glue the sawed off parts back and no harm done). Adding joints to the resin sounds trickier and I would not count on anything "popping" into the resin: unlike plastic the resin has basically 0 elasticity, it won't stretch to accomodate anything larger than the hole you made.
