Question: loading code when two packages are load?

[Qiantan Hong]

I’ve been working on the integration of crdt.el with a few other packages 
(xscheme.el, comint.el).
Those code only make sense when both crdt.el and the “client” package are 
loaded.

Is there a way to lazy load those code?

Currently I (require *client-package*) in crdt.el but that causes all client 
package to be loaded
when crdt.el is loaded.
Or I could remove the require but then that leaves bunch of free variable 
warnings
(because client package haven’t been loaded) and bunch of command that is
invokable but not usable.

Best,
Qiantan