I suspect Stuart will still only put up candidates on the list, but that won't primarily be to avoid harm to the SNP or to the independence movement - it'll simply be because he knows that standing constituency candidates would be an even greater waste of time and money than standing on the list. There'll be some tokenistic complaints about the SNP not being genuinely pro-independence anymore, but the main line of attack on the SNP will be related to the trans issue, which is now Stuart's first passion and preoccupation. The vast majority of his tweets these days are about the trans debate, and independence very much plays second fiddle. Probably Stuart will pretend that the Wings party is absolutely essential to ensure that people angry about self-ID aren't "forced to vote for a unionist party", and we've already seen him carefully preparing the ground for that argument in a couple of blogposts.
It's a nonsense, of course. People overestimate the extent of the anger that's out there due to the Twitter bubble. I agree that the SNP are going down a foolish road on self-ID, but the number of votes they stand to lose as a result is pretty modest. A largely single-issue anti-self-ID party is unlikely to have enough support to be viable - and the same, incidentally, would be true of a single-issue pro-self-ID party. The vast bulk of the population don't care enough about the issue to allow it to change their votes - and, no, polls showing big majorities against self-ID don't disprove that point. Those polls don't measure depth of feeling. And even if there was a sufficient reservoir of support for an anti-self-ID party, a female leadership that could plausibly paint itself as feminist would be needed to take advantage of it. In other words, the right sort of party would look absolutely nothing like a Wings party led by the Reverend Stuart Campbell.
If you want the SNP to take a more moderate and balanced position on the trans issue, there's something you can do that is far, far more constructive than voting against the SNP next year and potentially making a unionist majority at Holyrood more likely. You can respond to the Scottish government's consultation on GRA reform HERE. The deadline is 17th March, and if you need a template response, one possibility can be found HERE.