Shatner did ask for a million dollars to redo the special effects before the "Special Edition" DVD came out but they said no. To be honest, nowadays they probably could do it for even less. And you know what, fans actually would probably eat it up. TFF is one of those funny movies that many consider the worse of the Star Trek films (certainly of the first 6) but many still have a soft spot for it.
But the special effects are horrifically bad, unworthy of a Star Trek film. Hell, some of the effects from the original series (the 60's effects) were better. I get what people say about directors cuts and so forth. But in this case it would be to fix something that really is broken. Let's face it. There's not sugar coating it. The effects are poor. Sure, there are other elements of the movie that are cringeworthy. But this is one they CAN fix. And probably not to expensively either.
As for the DE of TMP, I'm one of those that actually likes the DE better. TMP has always been my favorite Star Trek film. Robert Wise said himself he considered the original theatrical cut to be unfinished. When he did the DE it was the intent to fix it. They updated the effects in a number of shots, sure, made some corrections on mistaken scenes, but he also did some re-edits to fix the pacing. I actually liked the improved pacing more than the effects. I thought the movie flows much better now. But of course, that's just my own take. I'd love to see a Blu-Ray release of the DE (which the creators of the DE have said they have and can be done -- all Paramount has to do is call). I wouldn't be surprised to see that actually in 2019. Paramount loves to celebrate anniversaries and that would be a great way to do it. However, that being said, I would never take the original theatrical version off the market. People should be able to pick up their favorite version, whatever it is.