I have always thought or said 'for what has been spoken, so shall it be done!' this has always seemed better for me. Is there a right or wrong way or is it just up to each individual witch to fine her own style.
ANSWER - I'm not a fan of set spell words to be honest. To me language is just a way of vocalising your intent. Spell words help a spell because they allow you to think about the result you want and focus the intent into a specific direction. But the actual words themselves are unimportant. Or unimportant in the sense that other words stating intent just as clearly would work just as well.
I think a lot of witches get too hung up on the issue of choosing the right wording and they usually get hung up for the wrong reasons. It is important to use wording that isn't too vague and avoids creating "loop holes" in your magic but it isn't important that a spell uses archaic language or repeats set standard phrases. The whole "mote it be thing" is a little pretentious frankly. It's just an old fashioned way for saying "this is as it will be". Why people expect to get better results using Middle English I don't know. If anything not using the modern vernacular could cause uncertainty and misdirection in a spell. How many people automatically say so mote it be without being sure precisely what they are saying?
So no, I don't think using spell words that have more meaning and resonance for you is a bad thing. I'd say it is a very positive way of bringing your individuality to your workings and to getting your own intent out into the world.