I would not mind a younger person but in this role you need good connections in the football world, which is not easy to have. Experience, track record. especially post Pep era will be important as in last decade we did not have any issues or fraction between DoF and manager neither under Pellegrini. last we had was Mancini vs Soriano maybe, which ended in an ugly firing but we were in very risky FFP situation at the time, also new management wanted us to play different style.
it was a bit of luxury to have good friends in crucial roles who had no chance of falling out. that might change once we have a Txiki replacement working with Pep replacement where the relation will be much more professional. for example there seem to be fraction already between new guy at Barcodes and Howe over transfer targets, lack of transfers, who picks targets etc. while at Arse Edu seems to be on great terms with Arteta. then Klopp had issues as well which made previous regime leaving only to come back now once Klopp left.
Chelsea also interesting example of manager and DoF relation, Potters, Poch could talk about that.:))
also a great example at United of how not to do it over the last 10 years. Woodward calling the shots and then Murdoch and co taking over to sign Antony, Mount etc for a fortune.
Bayern themselves have issues to replace the a two loud old ones, Rummenigge, Hoeness they went through Kahn, Salihamidic since then now they have a 3rd guy and its not easy...
What we need imo is a guy taking holistic approach looking out for academy, improve academy further, have an eye on CFG clubs too, making sure style of play is up to standards going forward, and on top of that can negotiate big deals with big players and plan ahead in terms of squad building. its a fucking hard role and a complex one. I am sure we have a supporting department in place for all this, I would really love someone like David Silva to do it:)
whoever it is new DoF will have a big say in who can replace Pep sooner or later.