I really wouldnt do this if I didnt have something to say though, so forgive me in advance but I just have to say that every td, even if it is just a 'solo' version, should have its own unique memorable tower(S)
This reminds me of the time I tried making my own TD based from a Green TD map. Almost every Green TD map you find out there is unprotected, so its reliable as a template. I have a friend who completely changed this Green TD map. I tried it and it was pretty good, with unique units and balanced waves and creeps and wonderful eye-candy. The only thing I didn't know was that it was based from Green TD.
I will try yours too. Solo TDs are generally fun (but they are quite lonely after a while.)