The Spectrum version of Arcade Game Designer is due for an update in 2015 and significant changes are already underway. Gone are the 8 x 8 blocks which make up the screen, replaced with bigger 16 x 16 blocks. With fewer blocks making up each screen, far bigger games will be possible.
Other additions so far include beeper white noise effects and some changes to the way sprites are handled. Much more is planned, so keep an eye out for updates over at the AGD Forums and the Facebook AGD group.