I am happy with the list as it is, there are some sub-par choices in there, but that isn't unique to the Steel Legion, I'd also support some tweaks to the points of artillery batteries as currently manticores are better in the majority of situations making them an obvious choice, either bumping them to 275 OR dropping the others to 225 would be worthwhile in my book, that being said, I don't think the list NEEDS any changes
I'm happy to help out with playtesting anything that isn't ridiculous (and I don't think any of your suggestions fall into that category), but my approach would actually be to suggest people try some 4k games if possible, trying to make use of hellhounds/tank squadrons etc as they are, that will IMO have a much lower impact than on the 'activations are king' mentality of the 3k game... stuff like battle titans, slow and steady spaceships and beefy unit upgrades are far more attractive at higher points values (well, they are to me anyway) which is why I think sticking to the status quo is the best option. The 'people not taking unit upgrades' problem is not endemic to the steel legion list, there are plenty of rarely seen upgrades in the marine list too (vindicators, land raiders, hb razorbacks, dreads, captains, librarians) as well as several in the ork list or black legion as well.... I just don't think you can make them an attractive option unless you reduce the point values to silly levels which unbalances the game
Another issue is that the steel legion list ranks up alongside the codex marines, ghazgkull orks and biel-tan as our 'benchmark' lists, they give a gold standard by which other lists can be balanced, if we fiddle with them too much, we risk losing that standard somewhat, which is another reason why I err on the side of the status quo
okay I've said my piece