It would be nice to have an adjustable snap-to grid to guide and speed up precise object placement when making scenarios. The idea here is that the grid can be enable/disabled. Optionally, it can be set so that the snap-to feature only applies to objects as the are dragged after placement, or applies to objects AS they are placed, as well. The goal here is not to make things easier by limiting the options of the creator, but to make things easier through the provision of multiple tools and methods to choose form.
The purpose of adjustable grid cell size and origin is to make it easier to line specific objects up in continuous rows and\or columns, to create things like walls, tunnels, and corridors. Changing the origin of the grid would allow players to easily connect objects of varying dimensions, eliminating visual gaps and undesired overlaps.
With the option to alter the grid azimuth, you allow scenario creators the ability to create intricate designs that are perfectly lined up, without limiting their object azimuth alignment to the four cardinal directions.
When it comes to the issue of determining the snap-to points of objects, there are two options. One is to simple snap the center-point of an object to each grid intersection. It is my personal belief that this might make visualization a tad more complex than it needs to be, but I also believe that it may be the easier of the two. The second is to have the sides of an object (or its collision box/mesh) snap to the lines of the grid, with up to one vertical (y axis), and one horizontal (x axis) side snapping to their closest corresponding lines, while allowing the option to snap only one side in total, as well. This can be done either through a method of auto-detection (finding the nearest gridline and snapping to it), or the ability to switch on and off the snap function for individual axes (alt. axies). For example, one could enable snap-to for lines running the y axis, and disable it for ones running the x axis (which would, in actuality allow for freedom of movement ALONG the y axis, while being locked to a specific x axis coordinate).