[Format] Landless via /r/custommagic

I'm not sure if this is appropriate for this subreddit, since I know it's usually reserved for custom cards. But I haven't found a better place for custom formats, so… yeah, if anyone knows a better place, please link me to it. Thanks!

So, what is the Landless format? As its name suggests, it's a format in which all lands are banned. Specifically, it's Modern but with no lands allowed.

"But without lands, how do you pay for things?!" I hear you screaming. In Landless, you use the cards on the field to pay for more cards.

So let me explain via rules:

1) After drawing your initial hand, the usual 7 cards or less after a mulligan, each player puts as many of their cards face-up in the command zone. These are your "mana engines", and they can be permanents or non-permanents; they just have to be cards with a casting cost. You do not draw those cards back, so the more mana engines you choose to have, the smaller your starting hand will be.

2) You may tap a mana engine you own at any time to add one mana of each of its colors to your mana pool. If it's an artifact, it taps for colorless mana equal to half its CMC (rounded up). Mana engines untap as normal, but being in the command zone, they cannot be targeted by anything.

3) You may choose to tap permanents you control at any time for one mana of each of their colors. Or, you may sacrifice any permanent at any time to get its full casting cost into your mana pool, including color (so, if it were legal, a [[Chromium]] could be sac'ed for 2 colorless, plus WWUUBB into your pool; or just tapped for WUB into your pool). As before, tapping an artifact this way gives you half its CMC, rounded up, in colorless mana, or sac'ing it gives you the full CMC.

4) At sorcery speed, and only once per turn, you may pay 1 life and exile up to one of your mana engines. If you do, search your library for a card and put it face-up in the command zone; it becomes a mana engine. This is the primary way to fix colors if needed, but since it's replacing one engine for another and costs 1 life, it must be done strategically.

And that's about it! Everything else works as normal.

I have zero idea how well this would work out, but it's an interesting concept to me, and I'd appreciate everyone's input on it. I'm sure there's some seriously broken aspect of it (as in, "this would suck to play because [X]", not necessarily "this is abusable"); if there is, let me know, thanks. And just your overall opinions about it would be appreciated, too.