Advertising on popular websites is definitely a good idea.
As for inviting "knowledgeable" Shia members - the issue is that the more "knowledgeable" they are, the more extremist and biased they tend to be. Take a look at their popular refutation sites - like shiapen e.t.c.
And at the end of the day, what are they going to bring to the table?
Mass quoting of weak and fabricated sources in the books of Ahlul Sunnah? They've been doing that for years.
Rehashing the exact same arguments over and over again - how many more mut'a threads do we really need?
Are they going to quote from their own books? Most of them are too scared to do that because they know that no Sunni will take them seriously.
We had knowledgeable guys like Nader Zaveri - but the result was the following:
http://www.revivingalislam.com/2010/09/hadeeth-17000-verses-in-quraan-saheeh.htmlHe tried his very best to go against the 'ijma of many of the Shias top scholars, and tried desperately to revise history with his own twist!
Rather than admitting that this is an authentic narration according to Shia standards, and accepting that many of their famous scholars believe in Tahreef, he goes to great lengths to find any excuse to reject it.
I think the way this forum is is good enough - knowledgeable guys from Ahlul Sunnah posting up Shia beliefs and refuting them.
The open minded and balanced of the Shias will read this, and, at the very least, ponder for a bit.
This is how it worked for me - I bounced back and forth from a Sunni site, to a Shia site, comparing arguments, and wound up at the conclusion that Shiaism was wrong, and Ahlul Sunna were right.
As for the "knowledgeable" Shias - they prefer to post in their own forums, and on their own websites, and they have been advised by their own scholars not to engage in debate.
Wallahu A'lam