A lot of mods have troubles with Steam, and especially with starting their mods. A few methods exist, but they can be hard to do for users.
While working on Roma Surrectum, along with PatricianS from RTR, we've developed together a launcher that automates that, allowing the user to start the mod with different options.
This tool is a massive rewrite of this launcher, which should allow it towork with every RTW mods (BI and Alex too) out there, modfoldered or not. A few functions were only edited, and the rest is brand new.
Here is how it looks like.
The first time you start it, you'll be ask to configure the launcher. It will first ask for your Steam Account name, then for the name of the modfolder to use. If you are using Viking Invasion, you'll have to type vi. (If my memory is good). If the mod is not modfoldered, just leave it empty.
Once that done, you'll just need to select the engine you want to use (and that you have), the command line (-show_err by default), and click on start.
If you want to change your username, or the mod to use, just click on configure.
It works with both RTW and Alex, but no with BI yet.
The file consist of the exe, plus the background image.