The other big area for subsea is marginal fields: leased FSPOs for example or where you have a satellite filed near existing infrastructure that cannot be drilled from that infrastructure either becasue it is just too far away or because there aren't any spare slots on the infrastructure.
However, the big problem of subsea is the difficulty of any kind of well intervention (I thnk there are only a handful of subsea wireline lubricators available worldwide), which is why all the work into TLPs, mini TLPs, spars, truss spares, deep draught floaters was done to get dry trees into the deep water.