You don't want a bottleneck, in case this thing grows bigger than you've expected it to. That means something the scale of Bonus Round is out of the question unless you are willing to invest significant time and money in the project.
However, you don't want to marginalize your new thing, by doing it half-heartedly, via boring text dialogue.
The problem with live podcasts via special guests if you usually have to have the...live, and scheduling can be a nightmare, and you usually end up having to communicate via phone, which can cause problems when conferencing, and controlling interruptions from various guests.
I suggest a few things:
A. Marketing - Don't introduce this has a news story, like so many great attempts by Source have in the past gone relatively unnoticed. Basically, all the big stories breaking from VGChartz have come from other sites reporting, or diggs. In reality, this site is large enough to promote its own events, and you should at least have some sort of temporary site change to advertise the event, and to promote it as something larger than a feature, or news story. Look to other sites. How do they advertise their stuff? Controversy, large promotional banners on your homepage, buiildup of guests, mystery announcements, and interesting, original questions. Theme your questions around sales, of course, but also keep the marketing value in mind with how you phrase them.
My suggestions: DO NOT put all this effort into this, and then post it on the front page like a common news/review feature. Too many mind blowing source articles in the past, have fallen to obscurity from this common mistake, imho.
B. Non-live pre-edited podcast. This is a new trend that's gonna garner some attention sooner or later. You get the benefit of being able to edit and rearrange your live podcast to add pacing, as well as remove any scheduling nightmares. The downside is your "podcast" won't necessarily have interactive guests, but it will have some very interesting interviews, which your jobs will be to analyze in your own segment. Face it, you have some big names here, and you guys kicking out your opinions live will grab some attention(NPD). If you aren't live, you can have final cut on what stays and goes, which will be to your benefit, considering how real your enemies are.
Basically, you'll get a better, safer show, with the emphasis on your analysis of interviews and the past weeks sales results, rather the inconsistency of relying on the guests themselves. Hint: It's also much easier to give your opinion on a subject(or even criticize it) when a guest isn't yelling in your face.
Your workflow would be:
Monday-Tuesday Interview special guests behind the scenes, kick out adverts, site changes, hints, secrets of the week, and exclusives to the podcast.
Wednesday - GotoMeeting the podcast with your team, analyze the weekly sales and the interviews. Give exclusives on upcoming sales, hype things like "Wii passes N64" with hints in adverts, "Wii passes new milestone, find out on Friday"
Thursday - Edit for pacing and content. Add or subtract as needed, and create a slimmer, better show, that protects everyone legally and morally.
Friday - Podcast in the morning, sales at midnight on saturday.
Sunday is a day of rest. Also, schedule your next week via guests, questions, and theme.
You do the minimal work. Your show is a hit, it is easily scalable to add special in studio guests, as well as higher profile callin interviews.
Would a live webshow even be sustainable?