I think it would work. I considered this idea in my head for a future 300g tank.
One good thing about the sump is that it adds water volume. I heard it makes drip systems easier yo setup. Ultimately, I'd like to have that on my future tank so I could automate some water changing, though I'd expect you to vacuum the tank still.
If you use those ATI sponges , I think you should stack two, or maybe three high powering some by powerheads. I got the stocking idea from here:
http://www.americanaquariumproducts.com/SpongeFilter.html#sponge5pro
Though I bought my sponges from aquacave as they were the cheapest (plus they price match an give you an extra % back in addition to matching prices).
I run a regular Hydro V stacked on a hydro pro v powered by an Aquaclear 70 powerheads. I also run a hydro v pro run by an air pump in my 125g.
I don't need these as I'm running HOBs but I wanted to put the PH was current for my clown loaches and I wanted to have an airstone. I figured Id have backup filtration in case of a power failure.
The air stone sponge has a battery backup pump hooked up to it that automatically turns on if the power shuts off. If I'm home, I could hook up battery powered pumps to the PH driven sponge.
I clean my sponges almost every week. They draw up a lot of debris and these, along with my sponge intake filters means my HOB don't get as dirty.
If I eventually get a 300g or do big tank, I think I'd run a few of these as backups.
FYI, the pros are easier to bring out. The regular Hydro 5 is a pain to clean. Its pores are smaller so it captures a lot of detritus and is harder to clean.
This made me just think of how annoying it'll be to clean all those sponges.
Ive never had a sump but I've been reading into it and it seems like they are way easier to maintain.
Of course cost is another thing. Those sponges are gonna be way cheaper than buying a sump and the pump and media.
I wish I could trust myself to DIY a sump off a Craig's list tank but if I get a big tank I'll likely get a sump made. The commercial ones I've seen are 400-800$ for the sump itself. Granted those are expensive ones with room for refugium and protein skimmer. I haven't actually priced how much it would be to get a simple one for freshwater but for $119.50 you could have ten hydro pro v:
https://www.aquacave.com/hydro-sponge-5-pro-aquarium-filter.html