I personally, never use DoF. Only reason for that is, while they can find gems here and there. They do make a lot of negotiation mistakes like offering better playing time for a player that progresses every year, which forces me to deal with the end result or they go find 29 yo for 100Mil and that doesnt fit with how I manage teams. I'd never transfer anyone over 25 yo, but 80% of the time I only buy players between 16-19 and develop them myself.
Will it be realistic? I dont think so. Will it provide a challenge for you? Absolutely!
One thing I'd pay extra attention, if you are leaving transfers to DoF is that make sure his playing mentality is similar to yours. If he likes to park the bus, and you like to attack then (in my experience), they may focus on players suit their own style rather than the team's existing style.