A good way to buff laning trundle with out overloading the already decent jungle usage
Buffing 
passive king tribute for early and later might help him stay in fights longer. (trundles sustain in the jungle would feel unchanged since he already can full clear and be at almost full health.
Maybe increasing his healing at lower health might be an alternative buff.
for 
which is okay, but you lose out on early sustain if you do so. Starting 
or 
gives better sustain.