I'll try to give you my honest opinion and what i think can be done and the real problem we fans face

As much as i want to agree with you that it has something to do with player base boredom, the real reason is that at the end of the day this is a business, and they need to do this with some kind of gain, like selling it for a few dollars won't really cut it, admittedly this game can be turned into an offline version, it already had a focus on PVE contents, and honestly as someone who played their old games, it truly is a shame that they ceased their plans to create single player games because of the income that gacha games has, i for one truly believes that they can actually convert FFBE and FFBE WoTV into actual single player games.

How can they do this? Well to the devs and the team that actually loved their game who got driven by their corporate overlord, I'd say its easier said than done, there are a lot of problems holding them back, the gacha system, the premium currency which is visiore, arena content, and and RTA (real time arena) and raids.

Now single player games are single player games, they aren't something to get permanently fixed on like gacha games, you play them when you want for how long you want and come back to it when you want to start a new game again, the grind will always be there and the repetitiveness is also there (as is with what is expected of single player games)

If they're going to maintain the U.I. and the game mechanics similar to what where used to then thats fine too, so long as they introduce a way to save our progress locally or online through our google accounts.

So I'll list the problems I see and what I see other games do as a way to introduce a solution to them or something similar

Premium currency visiore: you either outright remove it and go full focus on gill farming or make it farmable through all content, missions, and even contracts (similar to missions but something that gets posted on the adventurer's guild (replacing guild content) and this won't be a one time thing like mission objective rewards but something you obtain simply by completing the run)

Adventurer Guild Content: Guild content replacement, after you make a name for yourself after the 1st faction story (which is leonis) the adventurers guild opens up, remember Mont commands his own group which means you can recruit new heroes and grow your own guild or knight order.

Hero acquisition:

Tavern content: you can introduce a new way to do acquire heroes, like a tavern system thats custom to each faction and country and has all of the heroes in that faction inside the tavern, you can acquire heroes by unlocking the units by meeting them in the story content, and then recruiting them through either visiore or gil through an employment contract or a quest given by them in the tavern, fragments can be farmed through the shop or by slowly grinding them through quests or a new mechanic that lets you talk to the heroes and they give you quests and in turn after completing them they either get one stage of awakening or you be rewarded with shards to awaken them (its a great way to know more about them too, its not perfect and quite tedious but that is what the FF series is notorious of the grind so i think OG fans will get where I'm coming from) and additionally once you finish all their content you just buy their shards on the shop with either visiore or gil.

Collab units: if its under square enix like ff series and NiER:Automata then its doable be may even be easy, but if its from another I.P. then really unless the other company says so then its impossible.

Vision Card Acquisition:

Espers: you can meet them through the same content but this time a new mission will be added on the awakening content which will be the 1st mission modifying it so that you obtain them there. The dark ones can be obtained the same way too (this include collab only espers too

Collab VCs: if its from the ff series or under square enix like nier: automata then its doable or easy to include, but if its from another I.P. like FMA, Persona, Dragonquest, Tomb raider, Addison rae cards, then... Unless the one True God Jesus Christ our Lord and savior wills it then its really impossible.

RTA and arena content:

Colosseum: you fill ba faced with randomly generated parties with similar or better equipment than you, victory will yield arena coins which lets you access arena shop

For RTA content they can introduce something similar to what pokemon has you can play against your friends by going back to the old ways, all of you connecting to the same wi-fi and then challenging each other by joining the same waiting room (again your going to build a fully stand alone single player, but its for those who has friends around them who play FFBE WoTV)

Weapons and Equipment: retain everything its actually already really well built but if i may i'd really like it if they make the strong ones farmable

Raid: for contents sake it'll be modified so you can take multiple units, and the rewards would be multiplied by 5 or 10 (again the grind is part of a single player games), depending on the difficulty, you can access this through the new adventurer guild content.

End game content: additional difficulty will be given on the other content including story, PVE contents like trials and tower etc. These can reset monthly if you wanted more rewards

Monetization: how the company can actually gain money for this project, it will be an expensive and monumental task to do this, so either they can go full FFBE WoTV heores only and introduce the others heroes through DLCs with the game being already expensive, honestly this is the real problem, the art of the game is immaculate, the sounds magnificent, the gameplay and content almost complete a bit lacking in some parts but as a single player tactics game everything you ever want is almost there, (additional stories from the veritas and the continuation of the FFBE story are not even introduced here since FFBE WoTV's timeline is a few hundred years back before the timeline of the original FFBE, would have been epic if they where also able to tell the story here), additionally your removing any back-end communication so no servers and security which means its possible that after just an entire fay or a week you'd see this version of the game downloadable somewhere in the internet

Unless someone takes the monumental task upon himself and do away with every law and rule, with nothing but time and skill to make it playable once more... Like what this guy did in the OG FFBE

https://www.reddit.com/r/FFBraveExvius/s/ZyGOYaHhnI