The challenge here emulates the similar problem at the nanoscale where instead of floppy fat balloons one may try to make a robot out of carbon nanotubes.

In a first life challenge the contestants are permitted to use as many balloons as they want to try to achieve the challenges goals. (They may prefer to implement designs that minimize balloon numbers to avoid the difficulties of leaks and pops.)

Balloons to be picked up and connected would have spots of double sided sticky tape as a means of joining balloons together. Of course it also presents the challenge of "letting them go".

This can be a tiered challenge with a grand challenge being a balloon bot that can construct a copy of itself.
A second level challenge could be reproducing some or all of the parts of the bot.
Viable challenges would also be getting the bot to construct any predetermined structure.

Exhibit in SL will need some further thought.
I will set up a media panel with a youtube video of some examples in action.

I don't see where to enter the project slurl