There are steps, stools and bath bars which, imho, never work exactly right on their own. Getting into the bath is OK but lying down, getting back up and climbing out is another matter. I never take a bath now, which I miss terribly. I was a bath-time daydreamer (a book, some Brahms or maybe Bill Evans...). Converting the shower room to a wet room has proved useful for my DH (stroke survivor) but I just loathe showering (how on earth do people wash their feet and legs properly - not to mention the tender bits?). I'll never get used to the rotten shower but there's no alternative (hmm, maybe two strong men doing the lifting?).
If you don't mind a lot of builders' noise, mess and expense, it might be possible to create a sunken bath, with built-in steps so you could walk straight off the floor down into the water. There'd still be the problem of the sit-down-stand-up routine, though.