Hi, Thanks :)
The biggest challange is, to me, finding the neccessary time.
Organising some project like this not that hard to do. I am using a project management software (my own) for my dayjob and have my way of organising projects anyway. Keeping track of a few ideas, features and the tasks connected to that is not as hard as it seems. The main thing when organising is to have a plan at hand, not just Plan A but Plan A, B, C and if needed D to K. If you feel like you are starting to become spontanous about decision making you should really stop working and start planning again. That is my best advice after years of professional project management ;)
The development itself is not as hard as it seems. As i started from scratch (except for the engine, Thanks Ebitengine Team!) i had all the possibilites that i needed. This is why i never really liked using Unity and other major engines: You have to adapt your way of thinking, your way of desinging to their workflow or submit to limitations because you dont want or cant do that. If you are very familiar with such engines it might be easier to do whatever you want.. but for me it was always a bad experience using this kind of programs for larger software projects.