The main issue here for me is not that sexy art has no place in comics (there's a full spectrum of comics from cheery cheesecake through the hardest of porn, that's true of ANY medium), but that Halo is a fully-rounded, highly regarded and largely unsexualised female character, one of the first in 2000AD's almost-all-male history - slapping her name on (to my mind) an unconnected bit of boob art to sell more prints is just very poor form.
Halo's other creator has written more than his share of pornography, both explicitly (Lost Girls) and implicitly (LoEG I'm looking at you), with other writers' characters that were never intended for that purpose. But with Halo Jones, a regular woman in a milieu desperately short of them, it just seems wrong.