On my 1979 the engine service access is acceptable for normal maintenance and fluid checks. Sure, it could be better, but it's OK with my 6-1 height and 160 weight at 66 years old.
Several things to consider: not sure when they changed the battery location to between the engines as my 1979 is, but if yours are outboard of the engines then you'll have extra "work" to check water levels not to mention changing them out. Same for generator location. On my 1979 the genny is slightly forward of the engines on the centerline. Access for checking/changing oil is OK but if you need to change the impeller it's tight as the floor above isn't a removable hatch. (On my to do list next)
Shortly after buying mine one change that I made was to hinge the outboard large engine hatch covers and cut them in half with appropriate reinforcing, and making it so that the forward most hatch opens first. In this way you can gain access to the outboard areas of the engines without having to move so much furniture. I also cut inspection "hatches" 10 inch square above each radiator cap on the heat exchangers so that I didn't have to open the large hatches to check fluid levels.
My oil changes are made easy as I have an oil change pump with manifold plumbed to both engines and genny.
Walk-in engine rooms would be great but just not practical on the 43. Actually, as I recall the original 70 foot motor yacht had similar engine access to our 43's, under the salon floor.
Good luck learning her and happy cruising! This forum is a great source of info and a huge knowledge base.