i would suggest to include Fdroid as a preinstalled system-app on FP Open OS. I think it wouldn’t be a bad idea to enable noobs an easier start with the OS, because then they don’t have to allow sideloading. I know, you can simply make fdroid a sysapp with sysapp mover, but then you need root access and it’s removed with every update…
There are different philosophies in the forum/the company/the user base. Just have a look around.
I for one wouldn’t mind taking the risk in shipping the FP2 with microG and fdroid and no Google services at all. Others think (for good reasons) that this is the worst thing to do, as it will confuse users and it will make the phone less stable.
From what I feel micoG and fdroid are seen as “hacks” (they are) that make the phone less stable and insecure. This is correct, somehow. That again, also depends a lot on the user.
But especially if you want to market the phone to inexperienced users that want everything to be working correctly out of the box and that don’t like complicated learning curves or to wait a while.
Or in short: FP markets the FP2 as a stable Google phone, I don’t think Fdroid will show up as a sysapp soon.
Update: Listen to @freibadschwimmer! I confused the strange abbreviation again. For me, non-Google OS is just easier to remember. I did not understand you were talking about the non-Google OS already.
For the regular OS @fp1_wo_sw_updates already pointed out some of the main considerations.
If you talk about the Open OS, you don’t need to root it again after updates, as it is rooted by default. For the Open OS there was a lengthy discussion about what it should include, where also F-Droid as part of it was discussed. You may want to have a look at the discussion: