In theory: yes. But in reality, i'd say: no.
H100i Pro has 2x fan headers for rad fans and one ML120 is rated for 0.22A. Using 4x same fans with Y-splitters from AIO fan headers (for push-pull) would bring the amperage to 0.88A (4x 0.22A).
Though, i don't think AIO fan headers combined can sustain any more amperage than MoBo fan header, which is rated for 1.0A. Due to this, if you use 4-way fan splitters, so you can connect additional 6x fans to AIO (with total of 8x fans), you'll most likely fry the AIO fan header and possibly damage the AIO even further.
So, you can risk it if you want but i wouldn't do this.
Instead, does your Dell PC case have 1x free 5.25" external bay? Since if it does, you'd have alternative method how to...