I legitimately feel the Smash community blows veteran chances far too highly, when Sakurai (and Nintendo as a whole) have avidly claimed they want DLC to feel like fresh material, and not withheld content. Veterans are the epitome of feeling like "withheld content." The claim that veterans are a safe pick is not even substantiated- there is no proof to say fans would want a veteran to return more than a newcomer enter. If anything, particularly to the casual player, Id say the
seemingly similar play styles of Wolf and Lucas would actually detract people from feeling they are necessary to purchase,
Additionally, Lucas seems to be one of the lowest on my veteran list. His own creator said his series is complete, and Sakurai has gone on record to state he is not very prioritized in concern with representing series' without a foreseeable future.
All that said, if more veterans get in (which of course, I don't think is unquestionable, just not the priority compared to new characters) I would list the order:
,
,
or
/
Depending on how reworked Mewtwo is, I think the possibility of a reworked PT really could happen, particularly since he ushered in the avatar character we see everywhere now in Smash (Robin, Villager, WFT). If not him, I'd say the duo of Squirtle and Ivysaur.
Ice Climbers is there because I legitimately think we have not been given enough data to know how much effort they were able to put into making them work in the game in the first go 'round. With more time to work on them, the technical difficulties may have resolved themselves in coding, particularly since Sakurai believed it could be done after his initial interview when he expressed they were still being worked on.