the thing is, when you make a script, it counts towards the 16k limit. So if you want to use a bunch of placeable appearances that don't have blueprints, your better off, making a placeable blueprint, as it counts as 1. A script blueprint counts as 2, because there are 2 files made.
Now there are work a rounds, you can make the placeable blueprints, export them as an erf, and put them into a hak, (that's how CEP added their blueprints) those I believe do not count in the 16k. limit.
Changing the appearance, is tricky, and most tend not to do it, instead they destroy the current, and spawn in the new. Even when just moving a placeable, most destroy and spawn in new. The reason, if the placeable is usable, it can become unusable.(broken)
To do what your talking about, changing the look of something over time, I would probably use a NESS system, where it spawns in on day 1, is removed on day 4, and a new object is spawned on day 4 in the same place, and destroyed on day 9, and so on. Since NESS does not have a spawn during certain months (like it should
'> ) it takes a bit of work to make it happen. For certain month spawns, (like snow covered trees in winter) I use a get month function in on mod load, and spawn at waypoints if month is 11, 12, - 3 spawn at waypoint tag ((very basic overview)).
hope this helps.