Glad to hear that I've won you over 💪
Yep, you know what, I will make the default weapon always be Pistol. It definitely feels the best before any research.
Actually kinda liking the "first one's free" idea, genuinely never thought of that... I think that would address a number of people's gripes without affecting the game's balance overall too much.
Stats before->after I would LOVE... and would also be very difficult for me to implement, believe it or not. It's hard to explain it properly/succintly, but the way stats are displayed is handled differently for each weapon - couldn't just simply get a before and after value for each stat for every weapon. I'd say this is on the "maybe someday" list.
Hovering over item and lighting slots up... is a REALLY good idea. Guaranteed I'll implement this (not sure when, but I'd like to have this in the next or next-next update)!
Selling/deleting items, admittedly, will (at the very most) be a feature in a future additional mode, but for the modes that exist, I intentionally want player item decisions to be permanent.
"Shop item locking" (freezing as you call it) has been suggested by a couple others and is on my todo list!