I think you're over-thinking this, or am I missing something?
If your script includes an 'on run...' handler then that code is run when the script starts. All script code must be inside this run() handler or inside another handler.
If your script does not include an 'on run...' handler then the entire script is treated as an implicit run handler and the script starts executing at the first statement.
Accordingly, in your example you have an 'on run' handler, so all statements need to be inside there, or in other handlers. e.g., either:
on run-- optional if all statements are to be executed
open (choose file with multiple selections allowed)
set script1 to load script (alias "file")
run scriptscript1
set script2 to load script (alias "file")
run scriptscript2
end run
Or the other statements must be moved to a different handler:
on run-- optional if all statements are to be executed
open (choose file with multiple selections allowed)
doSomeOtherStuff
end run
on doSomeOtherStuff()
set script1 to load script (alias "file")
run scriptscript1
set script2 to load script (alias "file")
run scriptscript2
end doSomeOtherStuff