All electronic. No springs, use weights and magnets. Power it by solar and LTO batteries. Double or triple redundant key sensors. A full redundant copy of the

All electronic. No springs, use weights and magnets. Power it by solar and LTO batteries. Double or triple redundant key sensors. A full redundant copy of the firmware and automatic checking and repair of anything going bad, or better yet an ASIC(I think a RISCV synth with samples in mask rom could still be cheaper than somw high end pianos...)