You say it is an engine for making RPG's. A game engine can do anything, 3D first-person-shooter game up to just some fancy mediaplayer. All begins from abstract classes, and specializes to things like certain sound or graphics API. It can support many of them.
Every game engine has a focus. The Unreal engine does FPSs, SMBX does Mario-style platformers, OpenZelda does Zelda-style adventures, and so on. With a lot of abuse you can make a game engine do some other style of game, with varying degrees of success, but there's still a basic focus.

Mine is on RPGs, but with the TURBU system being plugin-driven, it wouldn't be too difficult to adapt it to another game style once the first engine is finished.

At the present moment we don't know when or if we'll be adding SDL in the mix, even 2D can be done with OpenGL, using basic or GLSL rendering.
That's part of what I'm offering: those questions have been answered. I've looked at what's available, tried various different choices, and made my pick based on what works, from real experience actually trying to do it.

Lastly all of the functionality should be crossplatform from the start, and possibly usable on mobile or android platforms. Unless engine was specifically written with all that in mind, it would be difficult to adapt.
Why do you say that? The editor is heavily VCL-based, but the vast majority of the engine code is pure Pascal over SDL and wouldn't have much of a problem at all in being adapted to other platforms.