You should be able to create custom elements as Lua script files, put them in a special folder, and they will appear in a separate category for custom elements. There could be functions you define like collision with another particle (particle # in parameters) or a custom draw function (like with BOMB or different photon colors.) There could also be functions dealing with how it moves.
You should also be able to create custom views in Lua. This would be simpler; it would only require you to define a function with X and Y coordinates as parameters. Then you can use a function to find the particle # at those coordinates (or if there isn't such a function, there should be.)
a.)Will overcomplicate things. As if we need anymore "How do I do Lua" threads. b.)Results in n00bs who figure it out eventually posting mods with horrible elements. c.)Defeats the purpose of TPT, having a CHALLENGE to create things, you shouldn't be able to just conjure up whatever you need.