Well if we're adhering to the canon storyline, both a wife and (multiple) students don't seem to be happening for the new trilogy. Kyp Durron and Mara Jade seem to be out of the question, really... Thrawn's a good idea, but I think we might be getting something similar to him with Supreme Commander Snoke anyway.
Darth Revan could be cool if presented in a similar way as Darth Bane was. In the canonverse, Darth Bane is really the only Ancient Sith we know of; it would be interesting to see another old evil that embodied the peak of the pre-Banite Order. However, if this were to be implemented? Revan should only be a Sith, clear-cut evil, and must remain ambiguous and unexposed.
I think ideally the "Old Republic" stories should be kept simple and largely left to the imagination. Climatic as it may be, it should remain backstory and for the most part unknown. Bane and Revan should be "the" Ancient Sith to remember; neither started the Sith, but they were the darkest legends that upheld the greatest legacies.
I think the "Prodigal Knight" story shouldn't be as overdone as it was in the EU, and rather saved exclusively for the classic Ulic Quel Droma. His story should be the perfect parallel to Darth Vader; hell, it'd honestly be better if Exar Kun wasn't even involved. Perhaps his story could even be the reason that attachment is forbidden in the Jedi Order, leading in to the PT situation. It would be cool for Luke to learn his story along the road to the new movies, uncovering legends of the old Jedi Knights.
Vergere would be an interesting modern addition to the story. I think we really still have yet to see a philosophy-driven, non-Jedi, non-Sith Force User in the canonverse. It's honestly good that things are kept pretty black and white for the most part, as to not overcrowd or take away significance, but having one character like that to help guide and shape the new characters would be a cool twist. Perhaps it could really lead to the change in outlook of the Jedi Order and lead to the right ending.
Other than them, it's probably best to create new characters rather than stick to old ones, really.
Kir Kanos!
Also Kyle Katarn, though I'd keep him strictly as a Rebel Agent and not becoming a Jedi. Him as an agent was rather an interesting, was something new as far as a character that a lot of people knew. Also keep his Stormtrooper background, I liked that Kyle had to rely on his Trooper and Weapons training than the Force and a lightsaber.