............ most of the very good lenses will allways be rather heavy,
so do not hesitate to add a grip to your camera : it will be much
better balanced (among other advantages) This is what I did and I
am very happy with that.
I still have a Canon outfit, altho I mainly use Sonys. Before
adding a grip and heavy lenses to a Sony, as replacement
for the Canon outfit, I'd just keep the Canon and convert it
to a heavy bulky "mirrorless" outfit by adding a really good
hood-loupe to the rear LCD panel. Costs thousands to go
from Canons to Sonys, but only about a hundred to add a
hood-loupe. End result, either way, is a big bulky live view
outfit ... but the Canon also doubles as an SLR if you ever
have need of one :-)
OTOH, the Sony will also double as a semi-compact if you
just remove the grip and attach a compact lens. Either way
it's your "Gas Money" so let's keep the economy rolling !
FWIW I have a 19-35 f/4 for the Canons and I've never for
a moment wished to speed it up to f/2.8 and crank it out to
16 [nor 12 ! ! !] mm. It's bulky enuf as it is. I've never been
tempted to adapt it to the Sonys. Tho my favorite shooting
condition is darkness, I find lens speed useful for midrange
FLs but pointless for ultrawides [same for longish FLs]. My
silliest lenses are a 20 f/1.8 and 105 f/1.8 ... I always wind
up grabbing the 20 f/4 or the 105 f/2.5 altho acoarst YMMV.
And I don't mean to dump on your interest in 16 ultrawide.
I have an old 17 f/3.5 that serves occasional need and I'm
not likely to ever part with it. It's just that when you discuss
combining a zoom function, ultra wide angle, and a zoom
function, with or without the grip, the idea of switching to a
more compact camera body doesn't make huge sense :-(