It was worth it a few months ago, but perhaps not now, in the US. The kids was $2500 in the US earlier this year. I sold it with my old 1.1 motor/bat/TCU in it to a friend--who actually has a kid--for $1250. We basically split the cost of the bike.
By default, the Kids LSL I bought was NOT in Big Kid mode. I did have to have it changed via the Specialized dealer software. If you buy the bike from a dealer, simply have it changed before you leave with it, perhaps? I didn't know about all this and had to bring in my modded LSL and ask them...
Higher-speed kids firmware. I'm not sure they knew how to completely re-flash it, and/or they may not have wanted to, as that brings up serial number/product ID/warranty issues.
No problem! Good luck! I found the hardest part was getting the bolt holes for the battery lined up with the battery mount holes. I suggest using a small allen key to find and keep the holes aligned while you get it mounted.
I think all the bolts used in the LSL 1 frame worked fine with the 1.2 motor. The mounting hardware is slightly different for the kids frame, as the aluminum frame has a different mounting setup. That said, the bolts from the Kids frame will work if you plan to install the 1.1 motor into it...
They are not super hard to find in aluminum. I am just looking for the 170MM ones in carbon, which are either not available in the US, or really expensive from Bikeinn and others from Europe. I recommend getting the aluminum ones from Bikeinn. I got a pair from them recently.
Math is not my strong suit, but yes, I think you are correct. I will say this, though: I happen to have both the V1 LSL with the 1.2 kids motor upgrade AND a V2 LSL with a 1.2 motor. The top speed of 20MPH (legal in US) is noticeable vs the "hacked" LSL.
I have done the Kids > LSL 1.1 swap of motor, TCU, and battery and it works great. I was only able to get my shop to unlock 16MPH, so I might have to get that cool kiwi de-restrictor mentioned above. I have found it a little difficult to source the carbon cranks in 170MM. Here's a crazy...