If you can't use radiant floor heat, would you use a Panasonic Whisper Warm, or something like a Stiebel Eltron CK or just a cheap strip of radiant?  I personally think the CK looks nicer.

http://www.stiebel-eltron-usa.com/ck.html
http://www.amazon.com/gp/product/B004W26KNS/ref=pd_lpo_sbs_dp_ss_3?pf_rd_p=1944687442&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B004K4A3QI&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0G2ACNJ0NYT9JFS3C0BK

If I add the Whisper Warm to all of my bath fans then I think that disqualifies me from ASHRAE 62.2.  So if I merely put another spot heater in one of the bathrooms and keep one of the stock Panasonic fans then I can qualify for ASHRAE 62.2 based on the one bathroom.  It is kind of hokey because it's the same Panasonic fan but the addition of the heater disquailfies it from EnergyStar.

I'll have a separate HRV but it may not meet the hefty CFM requirements of ASHRAE 62.2 (i.e. not enough CFM), so I want to get there by my bathroom fans and then do what I want with the HRV.

Have you looked at electric kickspace heaters that fit under the cabinet in the toe space? Seems like that would be much less intrusive than a wall mounted heater and it puts the heat right at the floor.

How about just a basic radiant cove heater? I just went that route with a customer, Panasonic whisper green lite + a cove heater in place of a crappy old fan heater. No results yet for comfort, but no reason to think it won’t work. Cove heater will be on timer. Simple. Cheers, Eric

Electric radiant underfloor is easy to do in conjunction with new construction or a floor remodel and it's pretty lux on the toes.
Another option is towel warmers which make toasty dry towels in damp climates and warm the bathroom as well. Both are pretty easy to control with a timer.