1. $findfile works, but remember to include the depth to avoid mIRC's default of recursing through all subfolders.
2. Also, by using the same number to load at a specific position, the scripts end up being loaded in reverse order.
3. $findfilen gives the sequential number found, so you can use that to load the files in FIFO order.
4. $findfile shows the entire drive letter and pathname, so you can use $remove to chop the beginning to make it a relative path.
5. Not sure how much of a problem it will be to load a lot of scripts at the same time, especially if they have ON LOAD activities, so can use a timer to spread it out a little.

Code:
//noop $findfile(StartDir,wildstring*.ini,1,0,.timer 1 $findfilen load -rs $+ $calc(5+ $findfilen) $remove($1-,c:\Base\Path\To\Remove))