EDIT IN BOLD
You may have already heard of Globish, Basic English, both are subsets of the parent langauge.
Well, we have the first (that I've seen) conlang that is an obvious tp derivative that is almost a subset of toki pona, with 20 words.
Here's a mental puzzle-- it's well known that some of the 125 (124?) words can be restated in terms of the remaining. While retaining all the particles and prepositions--ie. function-y words, could toki pona be reduce to 20 content words?
esun = tomo mani
mani = lipu pi jo ijo
monsuto = soweli ike
jan = soweli pi toki mute
kasi = soweli pi kule laso
Each successive definition would have to stick to the remaining words in the word stock.
And finally leading to a 20 word toki pona.
Personally, I'm favor most of all "mu", which is a proper subset of toki pona which is suitable for pedagogical purposes and broadcast on Voice of America.
jan mu: mu la mu li mu e mu tawa mu
jan mu: mu mu pi mu mu mu li mu tawa mu?
jan mu: mu!
jan mu: o mu!
jan mu: mu?