So, for the next version, I'm working on removing the limit of 32 entrances in a level, and instead allowing any amount (up to the number of allowed objects, which is currently 128; I'm hoping to expand that too, but possibly not yet). Current level format (which would need to be revised anyway to allow more than 128 objects) only allows up to 32 entries in the window order data, but very few (if any) levels use the window ordering anyway, apart from those converted from Cheapo; in the absence of window ordering data in the level, it just works on the object ID order and although it's currently limited to 32, this is just an engine limitation and not limited in any way by the level format; thus this is the easiest thing to expand first.
In terms of allowing more than 128 objects / 1000 terrains / 128 steels; the latter two would only require a level format that supports it, but having no maximum on number of objects would also require modifications to the engine as well as modifications to level format; the way trigger areas are currently handled limits it to 255 functional objects (extra ones can theoretically exist, but would be treated as fake if they aren't windows, water, receivers, one-way arrows or pre-placed lemmings).
I don't see myself ever using more than 32 entrances in a level (I can't even think off-hand of any case where I've used more than 4, and even that's rare - most of my levels use one or two), and I'd think there'd be very few cases where more entrances would be a more suitable option than pre-placed lemmings, but it never hurts to have the option there.
EDIT: Okay, added that, and as futureproofing, I've also revised the way the trigger area map is handled, so it can now handle up to 65535 objects in a level (and like the old system, objects beyond this won't crash the game or not appear at all; they'll just act as fake if they're not one of the aforementioned objects that doesn't need a trigger area on the main trigger area map). For now, this will most likely be a purely behind-the-scenes change, though perhaps I'll work on implementing the support for a larger number of pieces soon...
EDIT: Eh. Started working on such a thing, because why not. Initially new format will support (in addition to everything currently supported) object/terrain IDs above 255, an unlimited number of pieces (instead of 128 each for objects/steels, and 1000 for terrains), and an unlimited number of entries in the window ordering (instead of 32 max). It's also more open-ended to allow me to add other stuff to it later without having to revise the whole thing, if need be. It's closely based off the current format, but with just enough modifications to allow for these things.
EDIT: Okay, implemented in the editor (not yet in the player). Loading and saving perfectly. For the majority of levels, the flexible piece count rather than fixed also results in a much smaller filesize (though I haven't yet looked into what the results are once compressed) - compared to the old format where all levels are always 10KB exactly; "Chocblocked!" (first Bumpy level in the LPIV demo) is not even 1KB in the new format, while the largest and highest-piece-count level so far is 7KB.
EDIT: Tested compressed. About a 20% smaller size when compressed for Chocblocked; while the difference is negligable on the other level (less than 1%).
Now, to add support to the player (including in the Level Dump option)...
EDIT: Fully supported by the player now. As of the next release, you'll no longer be limited to 1000 terrains and 128 each of objects and steels; nor to a maximum of 256 objects and 256 terrains in a graphic set (the graphic set format already supports more pieces than this, but until now the level format didn't).
The next question is - while I'm here, I should probably apply the same futureproofing to the level format that I have to the graphic set format, of taking into account potential higher-resolution usage.
