BS if double after double is allowed

Imagine a delicious game where you're allowed to double a second time. For example, bet 100. Get 7,2 vs 6. Double down (total stake is $200) draw a 2 (argghh!). Double down again for the original amount (total stake is $300).

How does BS change?

I think you would start doubling on things like 3-8 vs 4-6, even 7 vs 7?

There may also be times you'd double a stiff just to take another card (with taking an ordinary hit after doubling not allowed), especially if you could do so for less (similar to casinos that allow doubling, but not hitting, split aces).

Look at Spanish 21