Is gRPC suitable for my needs on highly limiting IoT device?

I'm working on secure IoT device and arose a need to implement remote service (Service for internal use). So I'm trying to find out if gRPC would be suitable to me. Since device being secure it gives a lot of limitations. All the user software on device runs in sandbox-like environment, so standard means to access file system, networking etc. does not work. I have to use provided SDK to access files and create TCP/TLS connections. Also device internally uses protobuf 2.5.0 so trying to add newer protobuf library creates confilcts. Another limitation is C++11 (GNU ARM 5.3.1 compiler) and I need to use provided IDE which creates specific package to upload to device. On the server side we also use custom TLS library which uses remote HSM for cryptography.

Is it hard to write gRPC networking and TLS layers suitable for my needs? Or is it not worth the hassle and I should look for different protocol (suggestions are welcome)? Is there any other pitfalls?

So far I found out that protobuf 2.5.0 does not have "google/protobuf/util/json_util.h" and "google/protobuf/util/type_resolver_util.h" so I'm limited to gRPC 1.16 which does not use those headers.