Vallen, considering the ideas you have and your vessel requirements, do you really think looking around discussion forums and performing minimum Google searches, will really yield you a suitable design? Plans for a 75' - 100' vessel will cost many thousands of dollars and this is simply the beginning of the budget. How many designers do you think are offering free or low cost plans to 75'+ vessels?
If it's a model to play with, well there's plenty to select from, though don't expect much by way of modern design. If it's an actual vessel, maybe you'd be best to hire someone that actually can contact the appropriate sources, for a vessel of this class and contract the appropriate firms, that can either develop one or offer a set of modified plans, from their stock design drawer, as you seem quite ill equipped to handle this type of venture. This isn't intended as an insult, but simply an observation, based on previous inquiries here and your seeming understanding, of what might be involved in a project like this.
As to modifying or scaling up a set of plans, well in a word, don't. If you have to ask why this isn't such a good idea, then you're decidedly not the person that should be performing this task.