Making a top-down game?? Thread

Hi guys! A few years ago I used to work on a Half Life 2 mod which was quite ambitious and since I was new to developing and working alone on it it turned out to be a failure. After that I told myself that I would never do developing again unless I find an actual team to work with. So, I was recently thinking about a new concept that I would gladly work on but first I would like to share my ideas with you. I definitely wouldn't work on this game before I don't find a team which would help me make a test level where we could implement all of the game mechanics. Originally, the main focus of this concept was melee fighting (similar to the Assassin's Creed fighting which includes attacking,blocking and counter attacks but this was supposed to be a first person shooter) but then I thought it would be much easier to make a top-down game because it would be easier to focus on the graphics of the game thus doing more work on the actual gameplay. I myself am not much of a developer since I can only work in the Source engine (basic level designing) so I would like to hear your opinions on the choice of the engine. Here's a short description of the concept:

Plot
The game is set in a fictional world with fictional continents,countries and magic. The story revolves around a country which is facing a deep social and economical crisis and 3 different protagonists who are fighting against the status quo as well as their own personal problems.

Gameplay
Top-down melee fighting, shooting, magic fighting, mecha fighting, exploring, puzzle solving, basic parkour movements. General gameplay inspired by Brothers: A Tale Of Two Sons, Alien Swarm. Puzzle solving inspired by Half Life 2 and Silent Hill. Fighting and parkour inspired by Assassin's Creed and Dishonored.

Style:
Steampunk

Structure
The game would be made out of three single player campaigns (one for each of the protagonist) and the whole story would have a deeper meaning revolving around the concept of how nothing is as it seems and how appearances are deceiving.

The last aspect of this concept is the tone and atmopshere. After the gameplay this is the most important aspect and both the atmosphere and music are heavily inspired by the anime series The Vision Of Escaflowne. I'd like to hear your suggestions guys...

What are you looking for suggestions on, exactly?

Also,

I definitely wouldn't work on this game before I don't find a team which would help me make a test level

No! You will need to do some work before you get a team. That's how the team knows you're serious, and it won't just die like so many other projects!

I'd say the biggest problem would be the choice of the engine since I've spent like 500 hours or so working in Source but I haven't learnt too much aside from level designing. Also, that work was dedicated to a hl2 mod so basically I didn't need to create new material in the early stages while this game is planned from scratch. I heard that Unity and Unreal are good choices but I barely know anything about them. I would also like to focus more on the game elements rather than the graphics and make a 7-8h long campaign (3 seperate stories) so maybe and episodic model would be more appropriate, like working on one story at a time?

If you barely know anything about them, research them. Keep in mind what they offer (including licensing!), and what you think you'll need.

The thing is, level design in Unity and Unreal is very different from Source, and they're also very model-based, far, far more so than Source. So a lot of familiarity would be tossed out the window. If you stick with Source, you may be more limited engine-wise, but you have your experience. Do some research, weigh your options.

Thanks, I guess I'll research them for a while...