SuStel:
> Okrand had recently added 
> -Ha' to an adverbial for the first time

So, do we consider this to be for us a license to place {-Ha'}, to whichever adverbs we wish ?

His general message has been, yes, adverbials can generally use -Ha', but there's no absolute guarantee that all of them can do it.

And where do we draw the line ? Why stop at the {-Ha'}, and not continue to other rovers as well ?

Because Okrand has specifically about and used only -Ha'. No other suffix has been used or even hinted at.

If someone writes something which 'oqranD never wrote, we say "don't do it, it has no precedent". but if there is a precedent, why not act upon it ?

Precedent and suggestion exists for -Ha'; it does not exist for any other suffix.

-- 
SuStel
http://trimboli.name