I’d swap out the 251e for the 223e controller and use the Arpeggiator on one of the oscillators. The 251e is not nearly as fun or immediate as the 223e and is more of a chore to program. In addition to not being as ‘hands-on’, it is a bit of an overkill for a system of this size although not a bad choice. Check out my 10-panel Educational system for inspiration.