You don't have to go all Mark Twain - with his a-hollerin' an' a-cussin' - to notice that certain words beginning with the letter a seem a bit unnecessary. Or rather, that the leading 'a' seems surplus to requirements and a tad folksy. Obviously I don't mean words like apple (or do I?) but words like asleep, arise, abeam etc. If he's asleep then he's sleeping. Why arise when you can just rise (up, if you must)? And as for being abeam - well, really. Abeam? This century? Might just as well be athwart for all the use you'll get out of that these days.
No. It's time we waved goodbye to these elderly stuttering affected affixationals. It's time to behead these words and get used to using the grown up versions. It's not as if this a-prefixing is still productive. It's dead in the water - it's not giving us any new words. If somebody's dozing, we don't say they're adoze. If we're resting, we're not arest.
We must take care though. There are various etymologies behind these leading as. It's not always the case that aX = Xing (where X is, for instance, sleep). So although 'he is adrift' is much the same as 'he is drifting', it doesn't work for arise. She's rising is not the same as she's arise. In fact, the -ing deal is quite rare. There are in fact many other semantic relationships between the word and it's a-prefixed form.
For example, wake and awake are clearly about the same thing (not being in sleep mode) but being awake isn't quite the same thing as waking. But we still don't really need awake since wake will serve. In this case its past tense, woken, is close enough. You may argue that woken draws undue attention to the act of waking, which merely being awake does not - and you'd be right. But we can always circumlocute our way out of that.
We can get rid of amiss too. If something's amiss, then something's missing.
Before you object, I'm aware of the subtlety. There's nothing doing any missing here, in the same sense that the thing doing the sleeping is the thing that's asleep. In the miss case they're two distinct somethings. But most people aren't going to notice so that's OK.
So far we've concentrated on verbs (to sleep, to wake, to drift, to rise, etc). Excising a-words based on nouns is going to be more difficult. How do we behead a noun, something that one may - instead of be - have? For example, 'he has a certain aplomb'? Well, we'll just have to invent plomb, won't we. And we can't fall into the trap of thinking that aplomb is just a contraction of a and plomb, because the word won't exist any more - brilliant! Two birds! Same goes for adjectives. I don't see anything wrong with standing with your arms kimbo.