The A bag fram has no Handle FWIW . a few Zip ties and a plastic basket attached to the bag frame
to have an open shopping bag holder to take the store's carry out bags may be useful..
and people have swapped in a bit of a riser bar into the S mast to get a skosh more clearance..
brake lever tips as long as you can turn the bars and not strike something solid with them you should be fine.
I have a messenger bag fitted to my Brommy Front Rack , so when I have something bulky ,
I take off the bag, wear it, and strap/tie down the Box or etc. on the rack and return home with it.
I'm considering getting a Brompton S-Type for regular commuting and errands about town.
since you are only thinking, no money down , yet, ... Why not just get the M bar instead?
Why prefer the Straight Bar version? are you Short?
NB if you buy the H bar version it is, at the Bar clamp High as the S mast, but the Hinge is higher up ,
so you can fit a Lower rise handlebar instead of the M bar and still not have the left bar tip hit the ground when the bar is folded down,