Hi permarblau,
I’ll try my best to answer your questions, forgive me if all I do is muddy the waters for you.
Your first question I’ll leave to others, regarding markers as well as numerical offset files (don’t use them myself as I work directly from Delft). But I have imported IGS files from Rhino, drawings of hatches, winches, pedestals and wheels, but it was a long time ago and I had mixed success but that was proberly due to my inexperience at the time.
ISO criteria, Delftship is first and fore most dedicated to merchant shipping, us yacht designers have to take second place so the basic criteria is for cargo ships and passenger ships of 24m on length or over. But as I have just found out (last week) that you can set the Criteria to any standard you like, its designed to be flexible, if your interested in yachts, this one will interest you, you can alter the wind pressure (any pressure you like) if you have Load Cases module and see what the heel angle of your yacht is under steady or gust conditions, depending how much sail you have up.
Surfaces, I’m trying to think of what other surfaces you would want, from a box delete 3 sides and you have a sail, from a cylinder you can make winches, if there is something special that you require and if Marven thinks it has an application in merchant shipping he will do his best to include it but remember Delftship is solely run by one person, unless the staffing arrangements have altered.
If you want to move multiply points at once, highlight the points you want to move and add an @ at the very front of (XYZ) the distance you want to move in the coordinate box, if it’s a minus number the @ still had to be at the front eg @-1.999 or @1.999 .
To my knowledge there are no restrictions in how many items you can add in loadcases but I better leave this one up to others to answer.
I will add one other thing that might interest you, I use Delft hull modeller, Tanks and Loadcases and I do my interiors and detail drawing in Rhino. Although the tank module is over-kill considering I only design small yachts but I love it.
Why you may ask or ask not, I can create a tank in the keel which has the exact shape as the keel sides and fill it full of lead or and other material you like, and if you know someone in the Russian mafia you can fill it full of spent plutonium and you can add that one into Loadcases and call it the Comrade Stability Criteria.

Dasvidania permarblau