What you said about visas is in fact more complex in reality.Let's suppose that an FT without a Western university 4-year degree wishes to teach in Shanxi legally.He cannot,it's as simple as that.Why not? Because all Z visas for said province are issued by Taiyuan.So if Taiyuan has a policy only to issue Z visas according to the guidelines from Beijing,ie to degreed louwai,there's no way non-degreed louwai can get a Z for Shanxi.But unlike Z visas,F visas can be issued by the Foreign Affairs Offices of any Shanxi city.And some of those FAO's will do so,knowing full well that the recipients are teaching!Of course this is illegal,but China is China!

As for louwai teaching on L visas,most louwai can only get short-term L visas which cannot be extended.But in Shanghai,and some big provincial capitals,some louwai or their potential employers have forged special relationships with the FAO,and 90-day L's are available,extendable no problem!Louwai with Chinese spouses can also get long L's,extendable no problem.

When you spoke about TC's,I'd agree with you that most of them cannot get Z visas for their FT's.But that's usually because their FT's are non-degreed louwai.Long,extendable L's are usually also out of the question,but 90-day F's,extendable for up to 1 year is often the route taken.

There are some advantages of working illegally which no-one has mentioned.Your employer dare not cheat you.Why not?Because if you expose him to the authorities for employing you illegally,he'll be fined an arm and a leg.You'll be fined too,but at most only a few thousand.In reality,it'll never come to that.The employer will back down.

And what's more,some schools have been badly let down by dishonest louwai,who promised to come,but didn't.Maybe they found jobs in their homelands at the last minute and changed their minds about working in China.Then the school has a huge problem.To hire sb legally from abroad is a slow process.In contrast,sb in China on an L can be hired at once.Chances are,he'll be well-treated,as he's got the school out of a jam!

My up-to-date info is that Hebei and Shandong will still issue invitation letters to non-degreed louwai living abroad.But Beijing and Shenzhen won't.It's likely that visa conversion for Hebei and Shandong can still be done from L to Z,but only if your L was issued outside China.As for the HK visa run,L to Z,I reckon it's a thing of the past.I'd be interested to know the current situation.I'm not too clear about that one.