While I shared the sentiment over the past few years of being irritated at the behaviour of my teammate's strategy, I've always been fine with it because in my own internal logic, the primary driver doesn't choose the strategy for the second driver. More to that effect, the owner of the team also doesn't dictate strategies, so while it was annoying that they'd follow the hordes of other AI cars into the pits rather than doing anything smart, I was fine with it as the 'character' I was playing wouldn't ordinarily do it.
Now we're team principals, it feels slightly different and that you should have a certain level of say. However, I imagine if you're in a title battle with your teammate, then you could give them a lousy strategy... although if you're willing to sabotage your own game then I don't see the problem.
The problem I guess is that the AI still won't do what you want them to do. What I mean by this is; say you choose particular tyres for their weekend and you choose an extra soft so they can have a second new-set run in Q3.... and they use that extra set in Practice instead. Or you set their pit strategy to a 3 stop S-M-M... and the AI calculates and realises that a S-S-M is faster... then it'll reprogram it to the faster strategy (as it probably should). Or a safety car comes out on lap 19 and they don't pit because you've said it should be lap 21 and they then pit behind the safety car and drop to the back.
I think the role we are at the moment, Team Principal is different to the one that will dictate strategy too. I'd say it's probably a triumvirate of the driver, the race engineer and the Head of Strategy that will choose the strategy. Maybe i'm wrong but I just don't imagine Christian Horner working by candlelight and crunching the numbers himself.
I think the idea to have more control over your teammate is a decent one, but i'd prefer smarter AI all throughout the field. Where all 20/22/24 drivers actually react to each other in a completely logical way rather than all pitting around the same time. However, I get that they're just doing what is calculated to be the fastest race, but some more over/undercuts would be nice.