As i have heard, there were 2 types of e's, one got creating through connecting "a" + "i" (which i think is the e for 已然形) and one through "i + a" (which i think is the e for 命令形),
And since the suffix り apparently developed through fusion of auxiliary verb あり + 四段 in 連用形 (like 書き + あり = 書けり), that means it should be "i (as in kaki) + "a" (as in ari), which means its a fusion of 命令形 right? am i correct on this?