Heroes VII

They will definitely focus on (if they do focus on) creating content. A game save editor will clearly be one of their last priorities.

For the fifth game, they created a game save editor almost immediately (not as a mod, but as a separate program, but still). All sorts of tournament-related tools, which include game save editors, are the primary targets for modders for practically any game in the Heroes series. Of course, if anyone plays this game online, which in the case of the seventh game might be a problem... Although I don't have any statistics on that.

Yeah. Let's make Heroes 7 open source! The seventh game had some potential.

But Ubisoft probably won't want to open the source code... As far as I understand, even Heroes 1-4 haven't been made open source yet. Well, there might still be excuses that the code was lost, and so on... The fifth game could have been made open source a long time ago. But we have what we have.

all the remaining bugs,

Ugh, thanks for reminding me... There's all sorts of nonsense in it (mostly interface problems; I haven't seen such a mess in Heroes for a long time. A lot of obvious bugs remain unfixed since the beta test).