With an abundance of capable bats on this roster now, what do you want to see (not what you think they will do) as the "starting 9". The batting order is a whole other debate (..which can't even begin until you decide who is in the lineup), so lets just start out with each position.
SS-Semien
If you are mainly paying Semien to upgrade the defense up the middle, I think you need to let him help out as much as possible. To do that he needs to play SS. He's been a SS for years now, and is most comfortable there. I say keep him where he's comfortable. Then if he does well he will be apt to re-sign and become part of this team long term.
2B-Bichette
Bichette is a decent SS, but I think he could win multiple GG's in the AL at 2B and start in many ASG's. I think taking some pressure off him defensively will allow the bat to be even better too. That is his best tool, so that is what I want to maximize to it's fullest potential.
3B-Vlad
The key here is "opening day". I think after all the kids hard work (and the emergence of Rowdy Tellez) I think you need to let him at least fight for that position with Biggio and whomever else is in play in ST for 3B. I think he is going to show that bad week in the DR wasn't a true representation of his ability at 3B. He was better than what we saw in the error highlights 2 years go, and now he is in even better shape than he was then. ...and prob seen countless more GB's. To keep Hernandez and Tellez both in the lineup, Vladdy needs to play 3B. So that is where he starts the year for me.
1B- Tellez
He is a premium, premium left handed power bat this lineup desperately needs in it on a daily basis. Combine that with him being the best defensive 1B on this roster, and he is my "everyday 1B".
C- Jansen/Kirk
I see a 50/50 split between these young C's to keep em both fresh and on a routine.
RF- Gurriel
I know he won GG votes with his metrics in LF last year, but I think he could do even more of what makes him good in LF, in RF. He may have the best arm of all their OF's. I know it is different, but it's not like he as never played on the right side of the field.
CF- Springer
Don't need any reason here. He will be the opening day CF if he is healthy.
RF- Biggio
I had been thinking the addition of Semien may may Biggio the Util guy, but now I think they just need to find him a long term home in the outfield. They have a crowded infield already with more on the way soon enough. Due to his lack of elite arm strength, I think LF will be the best fit.
DH- Hernandez
I know they pay Grichuk twice as much money, but Hernandez is the guy I go with at DH if I am the coach of this team. I know he won a SS last year, but that just means he was a really good hitter. He has a good arm, but I don't see him winning any GG's out there any time soon. Combine that with the fact that thru 44 games last year he basically had an OPS of 1.000. He closed the season with probably his worst 5 game stretch of the year ( 2 for 19 with 1 BB) and then went just 1 for 7 in the 2 playoff games. If that guy we saw over the first 44 games is for real, he MUST hit everyday.
NOTE: Grichuk is able to DH or fill in for any of the 3 OF's. I think he could be the best 4th OF in baseball, and although expensive, gives them some real quality depth in the OF. This way you can also make a higher percentage of his ABs against LHP than when he plays everyday, which (in theory) should be a very good thing for him judging from his past splits.