I have most of the lenses you describe and have been using them all in working up my 645Z after ~4 years of shooting the D. So far I've not found any lenses that I was happy with on the D that fail to perform on the Z. So I don't expect that to be an issue for you either... if you like it now, keep using it on the Z and you'll probably still like the results.
As to the wider angles, nobody will really be able to advise what's right for you, unless you perhaps indicate a budget and whether you prefer to spend money or time. You've got several choices that essentially boil down to a trade-off in flexibility vs. cost. And that's assuming the new DA 28-45mm performs very well; if it doesn't, that option goes away.
I have the DA 25mm, and both the A and FA 35mm, followed by the FA 45-85mm. I won't be getting rid of any of them, unless it's possibly the FA 35mm if I ever decide to get the new 28-45mm. The A 35mm is too useful to let go of, and the DA 25mm has those extra 3mm that I sometimes really want on the wide end so I won't be letting go of it either. The DA 28-45mm has a flexible range of focal lengths + optical stabilization, and hopefully delivers excellent image quality. If so, it will appeal to me... but the cost is something that will slow me down from acquiring it given that I'm keeping the 25mm.
As for digital post like stitching and focus stacking, I do that all the time. But if I can avoid it by using a more appropriate lens, that's my preferred choice. I use digital multi-frame techniques mainly to do things the lenses can't do natively regardless of which lens.
