All good information, too much to quote.
Great idea but as mentioned you'll need a duplexor, unless you physically separate the antennas. Seeing it is just a portable setup this could work not the best and considering that it's just cheap baofengs I wouldn't worry about the long term damage to the receiver front end. There will be some issues in static and de-sense but it should work.
Go on ebay the controller box can be had for $50 from China.
Now with all that said. Your post mentioned 'legal'. Since you are using one of the few BaoFengs that are type accepted, you are miles ahead of the 'illegal' simplex repeaters on FRS freqs out there, and yes there is a lot out there. I really wouldn't concern myself with the fact that it may be a grey area with the controller box.
Of course not sure about where you are at and what kind of licensed Hams (aka: FCC Nazi's) you have around there. For myself, I just make sure that I have no interference issues and my gear is properly working. Personally I spent a lot of money to be as compliant as possible. (Something some Hams around here laughed at).
As for the ID, not needed. Just continue identifying yourself.
I got raked over the coals for transposing my Call sign once. I made it clear that they could feel free to call the FCC and then I could personally show the FCC the 4 'illegal' FRS simplex repeaters run by licensed Hams, 2 of them under the auspices of it being used for C.E.R.T. As well as, all the licensed Hams using the GMRS frequencies at power levels far exceeding the FRS limits, since they don't feel they need a GMRS license because they have a HAM license.
Needless to say, they tend to leave me alone now. I'm still the talk of their clique though, in the sense they don't understand why I spent all that money to have FCC type certified equipment, when I could have gotten by for a fraction of the cost with cheap chinese non certified gear. The fact that I am running a full duplex repeater at 30 watts is probably the reason I wanted to cross the T's and dot the I's as much as possible.
The only thing I have cheap is a cheap duplexor ($100) for now and the system is seldom in that configuration. (My repeater uses a Yagi to pick up signals from another town 12 miles away and rebroadcasts them out of a 5.2 gain omni directional, my reason for even putting up the repeater was interference from buildings in town, not a problem at the other one horse town. So I have to use space separation and notch filters for now, (eventually looking in to combining the signal into both antennas and seeing how that performs, leaving me with a oblong radiation pattern for travel between the two towns)