Isn't MM just sand with extra iron? I'm not sure. Is the point of it just to make your macros grow faster? Wouldn't that mean you're pruning more often?
Skimmerless is fine, it depends on the context and your tank management style/practises. I've done with and without. Generally speaking I like a skimmer better, but I find that going with "no skimmer" is less annoying than, say, going with a "skimmer that sucks."
I sure wish we could get eelgrass or turtlegrass from somewhere up here. AFAIK none of the Canadian vendors have any, if you find any please please please please let me know about it, I've been aching to try some for years and years now. I almost bought some last time I was in the U.S. but I chickened out at the last moment because I wasn't sure if it was CITES or not.
... Just noticed you said seaweeds instead of seagrasses. What kind of seaweeds did you mean? "Seaweed" to me means "macroalgae" (of which caulerpa is a type, of course). There are other kinds of macros though. Halimeda, Chaetomorpha, Gracillaria, etc. etc. Chaetomorpha (spaghetti algae .... I sometimes call it brillo pad or "green pubes" [since that's what it kinda looks like]
) is a nice one not prone to sporulation like Caulerpa and Halimeda are (only thing is it tends to be a bit of a slow grower unless under BRIGHT lighting like halides).