I feel "both parking a car or a bike" and "is be" are somewhat wrong. So let me change your sentences as follows. 1. If someone tells you that you may park a vehicle, you would think that parking either a car or a bicycle would be okay. 2. If someone tells you that you may park a vehicle, you would think that parking either a car or a bicycle is okay.
Yes, I agree "you will think" also works. But I think "you would think" works too. I feel "would" connotes "less probable" than "will", but I'm not sure. I too would like to hear native speakers' opinions.
When we talk about a subjunctive construction, I think it is easier to understand it without the 'inserted clause, I would think' becasue that way one can clearly see the cause-and-effect relationship beteween the conditional clause and the main clasue.
1. If someone tells you that you may park a vehicle, parking either a car or a bicycle will be okay. 2. If so