I render my own tiles using sprites... and it's virtually instant. The map generates as the screen/scroll position moves so it's only creating whatever the player can see at the time which stops the cpu being used too much at one time.
So it's definitely possible to do "manually" - if I can do it, anyone can do it. Lol
yes that's a way I already thinked about, the 'problem' of it is that in an isometric game, when you start placing the sprites in the layout editor you need to add from the top right to bottom left, otherwise you will have 'z' problem, you could obviously send it to back or front but imagine a canvas with more than 2000 objects, if you change one, you will have to change all the others after him, this as I said, in the editor... in runtime you can sort by Z with some few events but visually in the layout editor it will be a mess with things above others when it shouldn't...