It would be useful to have the ability to draw using dynamic resolution to create pixel art with varying resolution on a per layer basis. Have a look at Pixelmash by Nevercenter to see how it was implemented in that software. It works well enough in that software, but I think it could be implemented even better in Aseprite.
In the 1.3 beta, you can use tile layers for this, since each tile layer can have its own tile size, and you can use tiles that are solid-coloured. Use regular layers for your 1x1 pixel stuff, and tile layers for the larger stuff. You wouldn’t be able to have arbitrary mixed resolutions this way, though, since the tile sizes must still be a multiple of whole pixels.
I’m not interested in this feature myself as I dislike the look of mixed pixel scales, but if it’s not intrusive, it seems like a nice feature to have. If this is added, I hope that it’ll be a property you change through right-clicking the layer, rather than an additional input when creating layers, since it’s not relevant for most pixel art.
To make it work more easily with Aseprite’s existing system, perhaps rather than a separate resolution (which would get weird when you’re trying to edit Sprite Size or Canvas Size), it should be treated more like a scale factor on the layer, which you can change at any point. So the underlying cells are still treated the same as any other cell, with a max size equal to the canvas size, but they’re treated as more zoomed in based on the scale factor.