Since it's a Christmas time, I decided I'll play Santa and share the fruits of my work with you. So.. here it is: A Christmas Release of Retail-ation mod pack!
http://www.mediafire.com/download.php?7tdlzw3rb75yxuk
What's in it? Well:
-support for Ultimate Doom, Doom 2 and Heretic: Shadow of the Serpent Riders
-levels improved with some atmospheric effects
-both "episode selection" and "continuous game play"
-some bonus stuff - give it a try if you want to know the details!
Enjoy and Merry Christmas!
Posted 23.6.2012:
Hi!
Did you ever wondered what it would be like if ID would release their titles a few years later, past the "shareware era"?
Well I'm trying to answer this question with a series of mods for a few ID games, most notably:
-Ultimate Doom
-Doom 2
-Heretic
-Hexen
Currently I've made a first version of a mod for Ultimate Doom which adds:
1. no episode selection - all 4 episodes merged into single gameplay
2. intermission screens for episode 4 added (thanks to Skunk for it)
3. weather effects: fog added to the exteriors/some interiors + wind to the 4th episode's sky:
set the Graphical Options -> OpenGL Options -> Preferences -> Sector Light Mode -> Legacy
4. "episode-separators" intermission screens' backgrounds changed to episodes' ending arts
5. "shareware" related intermission texts removed/altered
The mod requires Ultimate Doom and GZDoom 2.5.0. The file is about 101 kB big.
Now I'm working on Doom2 + Master Levels + No rest for the living + XBox exclusive maps merge.

The features will be:
1. episode selection:

2. carefully selected mission pack's level order
3. weather effects: fog for most levels + wind for the skies
Planned is also a mod for Heretic, with the features similar to that of Ultimate Doom.
As for Hexen I'm not sure yet, will see.
Also, please get familiar with my other projects:
Classic Weapons Pack for Brutal Doom: http://forum.zdoom.org/viewtopic.php?f=19&t=33169
Statusbar Reloaded HUD: http://forum.zdoom.org/viewtopic.php?f=19&t=33397