I like the 0y format idea.

Your point about bit shifts is good, too. If the rightmost bit is the least-significant bit, then for consistency perhaps memory should be written with the lowest memory address on the right. Then 0xDEADBEEF makes sense both in terms of bytes within the value and bits within the byte; the first 4 bits within the lowest byte in memory are F, then next 4 bits within the lowest byte are E, the first four bytes within the second-to-lowest byte are E, the next 4 bits within the second-to-lowest byte are B, etc. So if 0xDEADBEEF were stored in little-endian, a hex editor could display DE AD BE EF