A couple of specific generalities
These are my personal ideas, which is what you asked for. In addition to my book suggestion above, as a result of your new info in your reply #6.
A 32 foot boat with an outboard engine just is not "right" and would not sell, ever, especially with a big, read: heavy, 25 hp motor. Folks with Catalina 25s have 9.9 HP 4 strokes that weigh close to or just over 100 pounds and they are seriously complaining about access, removal, adequate brackets and mounting. Older 7.5 HP 2 strokes were all of less than 75 lbs. The stern / transom may not be able to support that weight.
If you have a lazarette with a well that you can install the outboard, then seriously think about how the outboard will get hauled out of the water when sailing. Keeping it in the water in a well is not good for the engine, the shaft material is aluminum - bad corrosion. For instance, the Catalina 27 with outboard engines was designed for a certain size engine to be able to pick it (tilt it) out of the water when sailing. When engines got bigger, the old engine well wasn't adequate and many owner modifications had to be made.
A small diesel is appropriate for that size boat, and the simple shaft log and stern tube design has been around since they invented propeller shafts through hulls and still work quite well.
Determine if you're going "basic" or like bells & whistles, which will determine the details of any electrical support systems. Hand water pumps, hot water or solar showers? Separate wants & needs.
You really have to make up a design criteria before you even get started with the plans.
Young kids: a temptation to make as many berths as possible will end up with a claustrophobic boat with too many small cabins. Resist the urge. Either the kids will love sailing and you'll keep the boat, in which case it'll seem way too small with multiple small cabins; or the kids will hate sailing and it'll be just you and your wife or maybe just you - how many cabins do just (the two of or just) YOU really need? The original layout was probably a good sea boat, too.
If you plan an "historic" renovation, then that's something else, and your history research should be interesting, informative, and could be just plain fun. But then you will have to be pretty good with woodworking and materials selection or else the historic part will just be a copycat with no special cachet.
Like any boat purchase (understood that yours is already purchased, but you have a bare hull) YOU have to decide what the intended purpose of the boat will be and build for that.
And for goodness sake, please, don't put a Euro-style open V berth C270 interior in a nice boat like that!
Good luck, sounds like fun, keep us posted.