I have started work on a deck of cards recently and had an idea, and before I went through with this idea I wanted some feedback on the general idea first. So what this idea of mine is, is that instead of putting the numbers or the letters in the corners of each card you would write out the value. Like on the two of spades vertically down the card would be the word two followed by the spade like usual, so basically it would just be words instead of numbers on all the cards. So what is everyone's thoughts on this idea and if a deck did this would it add to or take away from the likely hood of you purchasing said deck.
Indices were created to make cards easy to read without having to see the entire face of the card. A single numeral or letter (or the two-digit "10") with a suit symbol is so quickly and easily understood, why would you change it? Adding words just complicates that and makes it easier to know when you've drawn certain cards - you have to fan the cards further apart the longer the card name is. "Ace", "two" and "six" would be close together while "Queen", "three", "seven" and "eight" would be further apart. One could look at the cards' spacing in sequence and have a fair-to-middling chance of guessing whether you're holding a straight or a straight flush.
It's better to have a uniform design for all the indices. Have you ever noticed that in a standard deck, the "10" is usually done sans serif and narrow, so the two digits of that numeral occupy the same amount of space as a single digit or letter from any of the other cards? This is a design feature, done intentionally, for uniformity and ease of reading.
I'm not saying it should never be done, but like any design conventions, if you want to break this one, you should have a good reason for doing so that fits the deck's design/theme somehow. A good reason would be an "all-letters" typographic design, with no numerals of any kind. But to break it just for the hell of it, because you were bored, because you couldn't think of a better idea, etc. - it would hinder the design and make it less popular among collectors and probably the general public.