In my time in Chinese Buddhism, I don't recall having heard anyone claim that somehow bhiksus are superior to sramaneras, who in turn ... etc. ... to lay women. In general, whoever has the virtues, compassion, wisdom and so forth, is considered highly.
It isn't seniority which dictates who gets the most respect? This is generally how it works in most Buddhist (Chinese or otherwise) organizations.
My point is that the laity are expected to defer to monastics. In the Theravada context, I gather from reading Ven. Dhammika's book, laypeople are even less appreciated. The first day bhikku is regarded more highly and listened to than the layperson of many years of practice and study. I'm not pointing this out because I want respect from anyone as a layperson, but just that the hierarchical system potentially erases the value of a certain demographic who might have something to offer. Laypeople might be valued as scholars, but not as dharma teachers outside of some Tibetan traditions.
In the context of transmitting Buddhism to the west, the lack of a meritocracy will turn off a lot of people.
The issue of seating arrangements has other considerations, too. For the monastics, the genders are separated. But, they are separated "east and west", putting the two genders in parallel. Then, of the men and women respectively, it is from monastic seniority in terms of samgha-varsa. One reason for doing it in terms of varsa rather than attainment, as the Buddha himself pointed out, is that it is clear and unambiguous. One can state a date for receiving precepts, and others in the community know without needing to ask, whereas who is going to spout about their own attainments? Nobody.
Historically wasn't it the case that the women sat behind the males?
If you're willing to change it into two parallel sections of segregated genders, we might as well go for equality and scrap the whole thing. We can all sit together, male and women, lay and not, without concern for seniority or title.
We are all, after all, adults and segregating people based on their gender is a throwback to archaic social systems.
Or should a monastic have to earn their position of respect from the laity by virtue of wisdom and deeds rather than by putting on robes and formally renouncing?
This is usually what I see being done, anyway. As the disclaimer above, this is just my experience, and everyone's mileage probably differ.
There are some eminent teachers nowadays who get respect heaped upon them and because so many people in their organizations are emotionally invested in them, nobody dares criticize them.
Case in point is Ven. Xingyun of Foguangshan who openly supports the death penalty and conscription, but still gets praised as some kind of enlightened bodhisattva. He might be a skilled administrator, but I doubt he has either wisdom or genuine compassion. Nevertheless, he is highly regarded by millions of people and anyone presumably becoming heavily involved in FGS will likewise become emotionally invested in the figure and not question his credentials as a "grand master" or even as a "dharma teacher". By default he has a position of respect simply by his role as an administrator, not because of wisdom. There are others who might not be in so high a role, yet write books about applied dharma, yet are in reality quite bitter and angry individuals. But nevertheless, they get a lot of respect just by virtue of their robes and title. I imagine they get published easier as well.