Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
It's engineering goals call for a (Linux) OS and hardware-agnostic platform, with transparent, free and readily accessible and modifiable code that can be also easily shared among users. The normal user has absolute control over the Sugar part but the core system remains secure from malicious activities.
One aspect that was explicitly stated in the OLPC project but is not even suggested by SugarLabs is environmental concern and energy (code) efficiency. The other aspect that was not addressed either by OLPC or SugarLabs is if free and accessible implies "as long as you do it a certain way".
With SugarLabs maturing and Sugar approaching its 1.0 version I think it worths taking a look at some of these trying to minimize prerequisites and established practices, and see a) if all these are feasible
b) if the implemented approaches can achieve them and c) at what cost.