It would solve the following problems:
- Bidirectional train stops, using two train stops, where trains can come from either side and load or unload using the same belt mechanism. This currently only works if the trains have an odd number of cargo wagons and locomotives, since an even number results in an odd total train length (e.g. 4 wagons/locomotives: 4 * 6 (wagon length) + 3 (gaps) = 27), which means that opposing train stops don't match up, and only 5 of 6 inserters are able to load/unload each cargo wagon.
- Train-to-train loaders, where inserters unload from one train and directly load into another train parallel to it. This only works if your trains are arriving in the same direction and you want to load/unload only the first X wagons, assuming they both have the same number of locomotives, or both trains have an odd number of cargo wagons and locomotives.
- If you've built a train stop for even-numbered trains and later want to change the direction that trains come in, you have to move the whole loading/unloading mechanism.
Changing the placement mode of train stops to allow 1-tile precision, like signals, while maintaining their 2x2 size, would seem like an easy solution, at the cost of only slightly more visual clutter when placing train stops (which we're already used to from placing signals).