Plumbing drains, water, and electrical were all VERY easy to run. 

I do know that some of the supply houses are great for lighting/electrical/plumbing/HVAC/etc.

I wouldn't put so much work into convincing them their bid is too high, put that energy into finding a better management firm.   

Instant water heaters take up less space and come in electric or gas versions.

I have seen properties convert the radiant heat system to electric board heating style during remodels.

When we do rent it out, we plan to add a flat fee for the included electric.

Are you going above or below ground with electric?  

Otherwise, the renters could be bitcoin mining or driving 2-3 electric cars and you’re paying for everything. 

No personal experience here but here's a helpful reference from someone who wrote a blog about different aspects of a 2 flat remodel in Chicago Scroll to "Two-flat journal 6: How to make an all-electric house" - - speaks a little about heat pumps and cost In the HVAC section.  

However, due to my college and career experience I can handle any of the electrical work while following the NEC.