Well, I think it's fine to swap alignment requirement if magic circle (or similar features) change from target 'evil' to 'good' (same applies to other features like smites with PrC's or feats which were intended for regular paladins). In regards healing blast we may need perhaps a feat tax overcome such limits. How sounds we expand Touch of Benevolence (http://dnd.arkalseif.info/feats/champions-of-ruin--27/touch-of-benevolence--2935/) feat; that it allows pick feats, features and even enter PrC's which are limited to 'good alignment'. However it never qualifies person for exalted feats and you cannot have vile feats while having said feat. It allows villain perform genuine benevolent acts without it making loose class features as well (like paladins of tyranny/slaugther), sort make more grey zoned morality on specific stuff. So it would allow villains to be healers and such (or this case pick healing blast).<br/><br/>Because of this spark though it makes it tricky for some spells targeting villains to work.