That's the thing yeah, if it's the team that owns the shares then yep you will be as sackable as the designer and mechanic. Its a bit of an odd situation lol!
To be honest i think this is silly, like i joined the leauge later then alot, i have made ground and also got stuff ready for S2, I think having objectives for a team that just started are a bit unfair, at least give 2 seasons before sacking!
How i understand it (and i may be wrong) is that when you sell a share you then become a publicly owned team (even if you still own 99%) and the board of directors will issue objectives at the start of a new season. Failure to meet these objectives will result in a vote on sacking you. But if you own more than 50% of the shares you would have to vote to sack yourself in order to get sacked!!!
I think you can be sacked at anytime if over 50% of the shareholders i.e. other players who have bought shares, vote to sack you. BUT you can also be sacked by the board of directors at the end of the season if you do not meet enough of the objectives they set you.
The problem comes when the objectives are way out of reach i.e your car is rated 8/12 and the objectives are to win the constructors and driver titles. Shouldn't these objectives be more realistic?