I suggest that you go to http://d2mods.xfernet.com and read up on modmaking.
The changes that you are looking for are very easy to accomplish, and you'll probably take more pride over playing something that you modded yourself. It might take a little time to understand how to use the tools that are needed, but after that it's a piece of cake. I warn you though, once you start modding it's hard to stop, and you'll probably never want to play Vanilla LoD again. :)
EDIT: I'm not sure about getting multiple mercs, and I'm pretty sure you won't be able to make rabies "contagious," but there are SO many things you can do. If you've never played a mod before, I suggest you try out one of the hosted mods on said site, you won't be disappointed.
The changes that you are looking for are very easy to accomplish, and you'll probably take more pride over playing something that you modded yourself. It might take a little time to understand how to use the tools that are needed, but after that it's a piece of cake. I warn you though, once you start modding it's hard to stop, and you'll probably never want to play Vanilla LoD again. :)
EDIT: I'm not sure about getting multiple mercs, and I'm pretty sure you won't be able to make rabies "contagious," but there are SO many things you can do. If you've never played a mod before, I suggest you try out one of the hosted mods on said site, you won't be disappointed.