I'm always out of the loop with indie games; now that you mention that Bastion... holy cr*p that game looks good.
I don't think it's a good idea to test scaling methods on an unfinished tile... you already know it doesn't look good, so you already start biased.
What I would do: finish rendering that tile; painting light, volume, color and texture to it, and when it's production-ready I'd be able to properly tell if it looks good or not when up\down scaled.
EDIT: That is, if Bastion even uses tiles. Judging from those screens it seems they painted the whole map as one unit. Too much variation and detail for any tile methods to compensate. There must be some tile logic under the hood for collisions and pathing to work, but the graphics themselves I think are represented by a single element (or at least whole layers, for some overlay and depth ordering effects).