[sqs]

I don't think it takes care of tone transformation (eg 他是 ni3shi4 -> ni2shi4). Or if it does, my tones are just off. But it's a really cool idea!

[carlmr]

他是 is tāshì which doesn't transform I think. Did you mean to write 你是 nǐshì? I think that transforms differently though. With the half 3rd tone only dropping.

The classical example is 4/4 不是. Which goes bùshì -> búshì.

Or 3/3 that becomes 2/3. E.g. 你好 nǐhǎo becoming níhǎo.

The 1/4 -> 2/4 transformation I think is specific to one. 一个 yīgè becomes yígè.

[jhanschoo]

The tone sandhi example you just gave looks incorrect to me

[jimz]

Well, OP wrote "he is" but then wrote "you are" in pinyin for one, and that's a bit hard to reconcile.