Extend Scratch with Custom Blocks (Bluetooth connection access)

Hi folks,
i would like to know if it's possible to add custom blocks coded via Squeak (Smalltalk) to Scratch 1.4 or the coming 2.0.

I'm a teacher for EDP and informatics and want to start learning programming with my pupils with scratch and an remote controlled model car (i-racer). Therefore i would like to extend an scratch project with blocks similiar to the motor-blocks for LEGO WeDo.

Or is there another way to send some custom bytes via Bluetooth from an Scratch-Programm to my I-Racer?

What I found so far:

Snap! (BYOB) -  but this seems not to provide the necessary flexibility to code the blocks with Smalltalk,  it rather provides a mechanism of organizing the existing blocks.

Panther - the CYOB function documentation looks like it's that what i'm looking for, but Panther seems quite quiet!? and the download page http://www.pantheronline.net63.net/download/ showed me an "403 Forbidden" message. Is this project stile maintained and where can i get it? 

Scratch 2.0 functions: looks more like BYOB - i could not find a possibility to add Smalltalk-Code to my custom blocks at the beta web site!

Anything good of these, for my purpose?

THX a lot in advance for your help! Regards Günter