Okay, I'm pretty sure I did do this last year, but I think it's reconfigured in my head since then. So.
What you need is one writer and three artists. Essentially, you decide to Form A Band.
And you decide up front that all the money from the anthology comic is divided 4 ways equally. This is for simplicity's sake -- people argue this point with me all the time, but I have had publishers say to my face that they avoid anthologies, especially creator-owned ones, because THE SUMS ARE TOO HARD. Keep it simple. 25% for everybody.
What you're going to do, you see, is one writer writing three serials for three artists.
You're doing a two-dollar book. That's FELL format. A 24pp unit, all on the same paperstock, including covers. "Guts" of 20pp, with the "cover", constituting 4pp, wrapped around it, yes?
Three 6pp episodes is 18 pages. Your cover and inside front cover for indicia etc are 2pp. So that leaves you 4pp, including the back cover, to play with. Use them to interleave the serials, use them as backmatter, let the artists take turns doing full-page pieces, whatever.
The cover art is a rotating job between the three artists.
Collect it every six months as a 128pp book (therefore still splitting everything four ways) or collect each serial on its own as best fitting (each book therefore splitting 50/50). (As is blatantly obvious, but people like to ask these questions instead of thinking for themselves.)
Go and do it. I need something to read.
Form a band, boys and girls. Form a band.