Why don't you use a skeleton key? They weight a lot less.
They can be insured and you can combine them up to 100 charges and they still only weigh 1 stone.
No need for this.
Skeleton keys and the Smuggler's Toolbox have you covered. (both are insurable)
Why do you have to get a smuggler’s toolbox from another player?
also, I have picked up a ton of skeleton keys for free, people rarely insure them so I regularly loot them.
We shoot things down when the need is adequately served by already existing items.
Skeleton keys can be frequently acquired through treasure maps. Lots of mobs drop maps. You could have a 100 charge key in an hour or two.
The toolboxes are admittedly a bit more annoying to get, but I've seen them as low as 25K. They're insurable and last forever. (~9 lock picks per charge and it auto recharges)
If the weight of lockpicks is your main concern, lobby for them to be made a fractional weight when stacked. I'd wager that most people would support that.
Let's not forget that the smuggler's toolbox gives only 5 to 12 lock picks per charge and it takes 24 hours to recharge just one charge. I go through that number of lock picks in less than an hour of playing in Khaldun when in thief form. The toolbox is not for serious picking of locks.