See Sprouting Fungus. Rare version.

DFC cards are always a bit of a mess to handle practically so unless you're really doing something neat like those 'walkers from origin, then I would rather not use them. For this example, I would considering opting for just exiling the card from grave and searching for a basic Island card.

I could also see using the aftermatch (sideway turned split card) tech here since the other side is a nonpermanent card and one a permanent card. Instant don't tend to linger too long on the board so there shouldn't be any memory issues there. You would also clearly see both sides of the cards so you have less of a chance missing that activated nonmana ability on the Shores side of the card.

You can't put split cards on the battlefield. Other than the stack, it has both sets of characteristics, so your suggestion puts an instant on the battlefield which isn't acceptable. Also, I'm not sure where you're getting the idea that DFCs are a mess. It's pretty straightforward, although Ixalan suggests you need something special to point out you can't just play the land normally.

Flashback costs have to account for the fact that playing a card from the graveyard is pure card advantage. This is a flashback variant in that sence. The land played from the graveyard should not have an upside in addition to being a basic land level land.

Mechanically DFCs are fine in theory. In practice however, just the whole process of flipping them over, recalling what each side does (reflipping to see what it does) and going around with proxies in drafts are all processes which I would call "messy".

@Secret, I totally get what you mean. I overcosted the front side, since playing from the graveyard normally would require you to cast an the spell in order to use it. If this were to be balanced for standard use, I'd probably add ETB tapped to all of the lands (or the mechanic itself) in order to make sure it isn't broken. But since this isn't strictly better than a basic land by itself, I figure not costing anything but a land play to play from graveyard is fine.

As for the split card option, it would be fine for this (if there was a way to orient it so that the land side would be played normally), but for the permanent versions the DFC would be clearer in showing what the current state of the permanent is. Ideally I'd have it as a pseudo-flip card, similar to Curse of the Fire Penguin, but that also limits the text space on the box. I agree with Tahazzar that DFC implementation is not the most elegant solution to the problem.