It would seen that the lid could be designed as a retrofit top for older tanks too.
Recently on my trip to Haiti we were enlightened to our bias when it comes to designing permaculture solutions. Toilets such as above are not possible in that environment, nor would anyone spend $500 on a toilet, let alone have plumbing, water, or a bathroom. Nothing is flushed away.
One solution is the movable pit toilet that collects humanure and when moved creates a area ready for tree planting. Incredibly the "porta-potty" had rain collection system built in that allowed for hand washing with clean water.
The Haitians, using what they had, created a solution that challenges even the eco-toilets. It creates a nutrient rich niche for food production and collects it own water (flushing not included).