This defeats the whole point of mindstars. You already get str->cun substitution on daggers as a rogue and the only benefit mindstars have is that they use different stats.
The main point of going mindstar for me is an additional much needed mindpower boost for AM and fungus.
I am not sure I would go AM/fungus for rogue, but that being said the winner who did this previously was AM (I think without fungus which is funky since fungus is 5x better than AM).
If I did go this route I would seriously consider superpower as a prodigy. But again the powers are stepped down to a very large degree and while its nice to have a portion of your STR be mindpower that contribution is minor compared to other things and SHOULD NOT be sacrificed for.
By far the main contributor to mindstar damage is the stats. Adding 30% will onto a mindstar is very significant. The extra MP from STR is nice but it will not make a huge difference even if you boost STR hugely which would require sacrificing other things and is not worth it. Getting say an extra 10-15 MP from taking super power is nice, but subsequently boosting STR past what is easily gotten is not a huge difference maker especially since Fungus does not scale to particularly greater effectiveness from that and scaling AM is not that strong anyway.
If one were to put 10 level point into dex instead of STR they would lose 2 physical power and 2 mind power if they took super power. That is a neglible drop in the bucket.
One could easily invest 10 into dext in the first 10 levels of insane and never touch dex againt and still have STR at decent level for a third stat with the remain level points and gear. In fact, you are almost certainly going to wind up with medium high dex ANYWAY because a lot of leather has STR with DEX on it.
Its really a completely moot concern.