Not sure why I didn't think of this before, but you can just copy all the .wrap files to another directory, and then instead of meson wrap install you just copy them to subprojects. That's how you lock the versions of dependencies.

meson.build

@@ -8,11 +8,10 @@ ftxui_screen = dependency('ftxui-screen')
 ftxui_dom = dependency('ftxui-dom')
 ftxui_component = dependency('ftxui-component')
 sfml = dependency('sfml')
-flecs = dependency('flecs')
 
 dependencies = [catch2, fmt,
   ftxui_screen, ftxui_dom, ftxui_component,
-  json, sfml, flecs]
+  json, sfml]
 
 runtests = executable('runtests', [
   'dbc.cpp',
@@ -33,11 +32,6 @@ roguish = executable('roguish', [
   ],
   dependencies: dependencies)
 
-flectest = executable('flecstest', [
-  './scratchpad/flecstest.cpp'
-  ],
-  dependencies: dependencies)
-
 myecstest = executable('myecstest', [
   './scratchpad/myecstest.cpp'
   ],