Right, because the D&D rules have been based on a grid system since 3rd Edition.Interesting. So any terrain would need to be gridded out, right?
In your honest opinion, do you think it would be worth it (from a creative, GM standpoint) to try and make semi-modular terrain, or just figure something else out?
I don't think it's worth it, honestly, unless somehow you KNOW that particular piece of terrain is going to get used a lot... and that's very rare in D&D. One of the things about D&D is that you go into a wide variety of settings and environments, and they'll be different every time. Even the super-modular sets like the Dwarven Forge stuff is only useful to a point, because the reality of how a dungeon is laid out can be really hard to simulate even when you have physical modules that are only 4 grid squares by 4 grid squares. My son has a DF set and he tried to use it a coupe times as a DM and got frustrated because there just weren't enough of the right pieces to accurately model the dungeons he was designing... which meant he either had to constrain his designs to what he could model with the DF set, or switch to something else entirely. So far, nothing has beaten the vinyl mat solution.