Characters - Image, Depth, Chemistry, Development

[endev8003]

I think Precia would've still been recruited as a mage and given proper training if the TSAB found out that she was a mage with power rivaling that of a lost logia long before she took up a job as a scientist. If not, then at the very least, keeping an insanely powerful mage within TSAB control would certainly put some people at ease.

Perhaps it's more of TSAB enticing powerful mages to join them and there are ones that decline. There are examples: Lutecia is a match for Caro, but isn't in the TSAB, while Caro is. Sieglinde from ViVid is also powerful and skilled, and isn't in TSAB. Precia might have declined because being a scientist is what she wants to do?

Nanoha's case in joining the TSAB kinda comes off as special not because of her reasons, but of her background. She's from a backwater planet that literally doesn't know of magic. Fate and Yuuno are technically members of a magical society, so deciding on whether or not to join the space police is as mundane to them as choosing their future careers. Nanoha's decision, on the other hand, will literally change her life, as not only would it separate her from her Earthling parents and friends, but she will also experience things no other human girl will ever experience in their lifetime.

Nanoha doesn't immediately leave her parents and friends behind. In the last episode of A's and the start of the StikerS manga it shows Nanoha as still going to school on Earth. Arisa and Suzuka is there, so it can't be a school on Mid-Childa.

I also don't think that TSAB will prevent Nanoha from visiting her parents and friends. Kind of like living in a different city or country from your parents. You don't see them every day, but you visit them and call them.

 

[Van Silverlight]

Welp, I can't help but see Nanoha joining TSAB was because she felt useless in her family or third wheel or lonely or whatever because of the movie.

 

[Akiyoshi]

There's the possibility Precia's astounding power is a result of her research. Remember she was dealing with AlHazardian science and The Garden of Time was a Lost Logia in all itself which also could explain her mysterious disease. Also she probably has similar problems as Hayate. She packs a titanic punch but only one shot Arf because she was distracted 
arguing. Even including her prowess in the games, again, Signum solo'd her there.

 

[Azure]

Isn't Precia someone with a Synthetic rank as a mage, just like Hayate? She is probably only a researcher and barely has any combat knowledge and can't really dogfight that much. So yeah, kinda like Hayate.