I agree, I think it’s possible but could end up being a really grim experience towards the end, especially if you start slipping north of 2 hours on the run.
Doing some maths, the 7 x 30mins run would give you 3.5 hours. Split up differently it could definitely yield results, for example the FIRST methodology where there is three runs a week plus cross-training. I’ve started using this myself lately (too early to comment on efficacy) but it breaks down to one track run, one tempo run and one long run. There is a significant amount of intensity so not really one for beginners, I have done quite a few marathons and ultras so have a good understanding of what I’m capable of.
I think using the 3.5 hours to do something like one hour on Tuesday, one hour on Thursday and 90mins on Sat or Sun would yield much better results, but probably goes against the spirit of what @Nate_Pearson was trying to say. Completion vs competitive is two different things.