i dump any cuttings with thickness larger than 1/2" from my trees. reason being a cutting, doesn't really matter how thick it is, it will put on a bud, or maybe more, and that will be the leading branch that will turn into a tree. doesn't really matter how thick the cutting is, they will all turn into a fig tree.
rooting is a children's play. anyone on this forum can root. anyone who's not on this forum can learn to root in 5 min.
as to thickness of the cuttings.. it takes about 2 yrs for a sucker on my VdB or Kathleen's Black to turn into 1" to 2" thickness. if you take the very bottom cutting, which i do not send out since they are 2 yr old cuttings and i prefer to send out 1 yr old cuttings, it will be of similar thickness. it doesn't really have much advantage over the top cuttings.
i don't have many fig trees.. only have around 70 of them. there are about 50 different varieties in them. 40 of them are known varieties from reliable sources. no guess as to what my trees will be. there are few unknowns and they will remain unknown until positive identification can be made, but they will be identified in my books as "member name's unknown".. like Joann's Purple Unknown".
now.. compare to most of the members here, i have very few varieties. jon, the moderator, has over 1,000 trees. he has most extensive collection this side of pond. but there are others with similar collections on this forum... with hundreds of varieties and more in number of trees.. some have very rare trees that most outside of this forum has not even heard of..
so to come here and "explain" that we do not know what we are talking about.. is funny :) i had a good laugh.