Nice to meet you Astus, we are brothers in the Dharma and please understand- my words may inadequately convey my limited understanding. Thank you for your response and I will try to clarify my meanings
In Chapter 2- "tactfulness" after the unreceptive members of the assembly leave, the Buddha says to Sariputra pointedly: "It is because of his DESIRE for all living beings to apprehend and enter the way of the Buddha-knowledge that the Tathagata appears in the world. This is the SOLE CAUSE."
This shows that without the compassion to teach others, there is no true Buddhahood! Full, Perfect Enlightenment is Buddhahood and is only gained by the 1, Bodhisattva, vehicle. Working toward perfection for the good of others, that is the only way!
When you said- "Enlightenment is someone personally realizing the ultimate nature of phenomena." I believe you are talking about an attainment of personal quality. The Lotus Sutra teaches that there are many levels of attainment here, all working within the 1 vehicle weather the individual knows it or not. The disciples know and profess in the Sutra that their attainment is not equal to that of the Buddha and this is the first deep truth of the Lotus Sutra: what was known before as "Nirvana" and what is alluded to in your sentence as "Enlightenment" is not the end goal but, part of the cosmic [i]process[i] of Buddhahood.
Secondly, the "Ultimate Reality" he is preaching about is spelled out in no uncertain terms as well- it is the fact that the 1 vehicle is the only vehicle. Active compassionate engagement with others in the world is the manifestation of true wisdom and understanding of the truth: the true nature of all is Buddha-nature. This is hard to understand and hard to accept, as shown by the story in the sutra of Bodhisattva Never Direct (Sakyamuni in previous life) that went around saying to all "it is not for me to direct you but, I suggest you take up the Bodhisattva career and become a perfect Buddha" and was given a very rough life for it.
The stage of this sutra is the whole of the cosmos and the cast is no less than ALL sentient beings. The historical Buddha transcends his own current manifestation to teach the second great point of the sutra: all living beings ARE taking part in the appearance of the Buddha in the world, weather they know it or not because they are the CAUSE of the appearance. We, by our practice of the Dharma, are taking an active part in the "playing out" of the Lotus Sutra and, our destiny is, as Never Direct stated, to become perfectly enlightened Buddhas. If we do not practice the Dharma, we still are participants in the sutra as causes for the Buddha's and Bodhisattva's practice