It depends what you mean by "simplification". The fact that phonics is something that can be taught and can be helpful for learning to read indicates that English does have phonetic spelling rules, inconsistently applied as they may be. It would be possible for a spelling reform to preserve the existing spelling conventions of written English while simply making the rules more consistent. There aren't really that many outright ambiguities in written English. Sure, <a> can indicate a bunch of different sounds, but it's usually possible to tell what sound it is from the surrounding letters---e.g. it'll be "short" (as in <cat>) if it's in an orthographically closed syllable, and "long" (as in <name>) if it's in an orthographically open syllable. The trouble is that we have words like <give> and <many> which are straight-up exceptions to the usual rules about open vs. closed syllables (<many> also has an exceptional sound value for the <a>). Respelling these occasional exceptions (I'd go for <giv>, <menny>) might make English spelling considerably less confusing while still preserving its basic "look and feel".