The popularity of English can be a double edged sword for English based 

One of the good sides is that there are lots of people who would like to 
learn English but can't because it requires too much of their time and 
money to attend courses. It takes a lot of resources to teach and learn 
all those irregularities and other difficulties that English is so known 
for. Another good side is that the IAL could be used in practice right 
from the start with people who speak real English. So the idea sounds 

A clever design of English based IAL would include the simplifications 
that George mentioned: systematic spelling, regularized grammar and 
reduced vocabulary. Perhaps some light phonological simplification would 
be needed too. Unfortunately the popularity of English puts all these 
clever improvements into peril. As long as real English is the most 
popular form of English it will corrupt speakers of IAL English with its 
irregularities, idiomacies and lexical excessities through movies, 
music, websites and other media. How could learner's of IAL English know 
what's IAL English and what's real English? They would pick words, 
expressions and even spellings from anywhere, not only from some 
official list of 1500 root words approved by the IAL English academy. 
Soon IAL English in actual use would be full of "realenglishisms", and 
that would ruin the whole thing.

The only sure way to safeguard English based IAL from bad influence of 
real English is to make it so different from real English that there is 
no chance to confuse them. (Dana's Ingli seems to be something like 
this.) Unfortunately the less English based IAL sounds and looks like 
real English, the less it can benefit from the popularity of real 
English. The result: nobody is interested.

Risto Kupsala