So in my environment I have the TSM server with a small TS3310 at the main site.
Offsite I have a TS3500 library greater than 5 miles away.
We are using straight FC. Keep in mind, depending on the LTO drive, you may need to look at the number of links you have available, or you will hit performance issues. Especially if other people start to hitch a ride on your links. Depending on how far away you are, you will need to invest in the right equipment to drive long haul optics. You'll want redundancy so you will need multiple routes in the street. You don't want both your fiber pairs running down Main street to get taken out by construction (happens more than you think!).
I have no experience with FCoE, and the few times I brought that up, my network team states 'Keep your fiber off my network'. Will state that our Ethernet network is running over the same fiber in the street as our FC is, so if you have extra pairs or waveleingths, it shouldn't be a problem to add on. Nothing against my network team, they just don't want to manage the SAN side of things. Their hands are full with day to day core routing and the likes.
So in short, yes you can do it. There is going to be cost involved, and depending on your resources the cost could be expensive. Last I knew, to drive our 8gb FC for 5 miles was 20k USD per laser. Plus the various interconnect fees for termination, and likely a whole bunch of other stuff that I am not privy too.
Biggest con is make sure you have enough capacity to utilize the number of tape drives.
If its a cold site, you will need to plan on visiting it to load cleaning tapes, scratch tapes. Monitoring the tape library also becomes important, make sure you have a way to remotely manage it.
My team and our infrastructure is great and I never have any issues communicating to my remote library. The issue I have is the performance. (See my various posts talking about performance). The expense can be...well...VERY high. I cannot stress this enough, if you don't have the budget to get the required infrastructure in place, don't do it. I don't have any equipment recommendations, but you'd likely want to go with the big name networking companies for SAN and Ethernet so you have that level of support. Don't use the cheap stuff.
Keep in mind, a single 8gb hba can drive two - to two and a half LTO6 drives at full speed, assuming the disk storage can keep up. Look at your tape drive specs, how hard can you push your storage and use that to help figure out how much capacity you will need, and then see if anyone else will be hitching a ride on your links!
I hope this helps. I know, there is a lot more to consider what I posted here, but my wish is it gets you thinking on the right track.