The big thing about buying boats, like any major purchase I suppose, is compromise. I have seen a couple of Yachtworld listings where owners have done various modifications that added steps to swim platforms. A few were nice (and looked expensive) others just looked bad. Remember that there can be a lot going on in and around a swim platform. to take up a lot of space with a staircase of some kind might be more of a pain in the ass later on.
There are cockpit sundeck trawlers out there. Defever, Tollycraft, and Carver (or was it Bayliner) make them, however, you often will still have to climb a ladder to get to the sundeck. There is no easy solution I don't think. Sundeck trawlers are what they are. We loved ours (so did everyone else... party central).
We always just carried a lightweight plastic ladder with us and boarded from the side.