There's room for 3x 120mm fans in front. The drive bays are removable. There's room for a 240mm AIO. The only thing that looks to prevent that is the length of the psu shroud. That's fixable in 2 ways. Forget about the shroud, or chop it back 3-6cm. This would give the aio room to mount internally, still mount 3 fans in front/push or 2x internally in pull (better actual idea), provide airflow and definitely work better than any single cooler that'll fit in a 155mm space.
That's what I'd do, but I'm sorta handy at cutting metal clean. To finish off the edge, either file it nice/paint it or use an automotive car door edging or similar.
Your choice, your case, you most definitely do not have to stick with what the manufacturer has left you with.