Hi svarrer,
nice start of the plugin loader...
I have some additional suggestions...
don't call the language files [xx].php but plugin_[XYZ]_[xx].php
con't call the configuration file config.php but plugin_[XYZ]_config.php
the reason for this is that (in the future) we can separate CMSimple configuration & language settings from the plugin config & language settings...
Also change the cf & tx prefix to a unique one for each plugin
Code:
$adv_mf_tx['receiver_email']="Receiver e-mail address";
$adv_mf_cf['required_field_labels']="Name,Phone Nbr,E-Mail,Comments";
$adv_mf_cf['required_field_names']="name,phone,email,comments";
I'm currently programming on this kind of settings from the administration panel... (in function of an advanced mailform plugin)
I have both plugin settings for config & language in a separate .php file in 2 different subfolders of my plugin main folder...
And it's already working (just finished it right now...)
The mailform is based on formmailer.php - I just need to program the dynamic form layout from within the administration panel...
If you want me to send the code, please let me know via PM
Nice to see that my idea about the plugin addon wasn't that bad
JAT
PS. tested the plugin loader already

included the an admin.php & index.php file in the root of my plugin folder
so far my plugin works fine (as far as I could test...) also the admin is nicely added in the administration page...
Does this mean you're gonna rewrite you cms_packages as well ?