Best way to build/support tiers on this offset cake?

no no no--you'll be fine

just kind of center your focus on the parts of each tier that touch the tier below it--and don't look at the parts that hang over--place  your supports under each of those tiers perfectly balanced just like any other cake

the supports will be centered under the tier it's holding up--but they will be placed off center of and into the tier below it--but it all works--so long as it's centered under what it is supporting you will be fine

each tier's center point can be balanced on the dowel supports below it--it's still balanced weight wise

i'd use 1/2 inch foam core and i'd wrap my fondant over the edge of the board 

i wonder if those are dried fondant panels over those paisley eyeball things

that is a really cool cake!!!

the doweling is still kinda nervey though huh--but it does work

and those are brilliant sharp edges everywhere

good luck with that!!!

it makes you wanna go and put your hand under some of the tiers ;)

it's compelling in a good way

here's an idea for really nice sharp corners--

first be sure the cake is perfectly level from corner to corner--build up the corners with cake if necessary

trim the edges of your cake--just shave them so they are smooth--just a little trim to remove the extra bits

you can get the icing on smoothly and efficiently this way

on the corners, take a piping bag and pipe an additional fat stripe of icing up each corner

then scrape off the excess with a nice straight edge (like a plastic scraper or dough cutter) to reveal the nice sharp corners

it's kinda dark in the link but see how the icing on the edge is real thick and real thin where the cake bobbles and weaves on the outside edge?

hold a piece of paper up to the computer screen to the edge of the cake to see how much to trim off

https://www.hersheys.com/recipes/recipe-details.aspx?id=184

some cake compatriots will poopoo this but

this is not the design to figure you can fill it in and build it up here and there with the icing--

an uber level surface would of course ensure the cleanest sharpest results

how sweet of you--thank you!

You will be fine! Just add more supports where the cakes touch and make sure to have a center dowel inserted in the (almost) into the middle of the cakes.