I consider online domination as what you describe under 'Crossover activities' and Roleplay.

You should of course talk about what you both want in an online relationship and see what the possibilities are. If you find that you can enjoy playing together, then you can engage in assigning and doing tasks and describing to the other how you've done it and how you feel with it. The assignments can be either to do immediately while chatting or they can even continue between chat conversations. This way the Dominant can exert some control over his/her submissive and later hear the results, perhaps with photographic material to support it. As long as you both get your fun out of it and enjoy yourselves!