What are the limitations on powers usable with Unleash Spell Power?

Question

The Spell Commander Paragon Path, described in Dragon Magazine 381 and available to Artificers, has the level 16 feature named Unleash Spell Power, which has the following text:

Unleash Spell Power (16th level): Whenever an adjacent ally would make a basic attack, that ally can instead use any 1st-level arcane at-will attack power they know. The ally must used [sic] ranged powers in the place of ranged basic attacks, and melee powers in the place of melee basic attacks.

While its effects are obvious in most cases, there seems to be some ambiguity when it comes to powers that simply grant a "basic attack" without specifying melee or ranged. While obviously either Melee or Ranged attacks are valid, what about other types of attacks?

e.g. A Sorcerer adjacent to the Spell Commander is granted a free basic attack from an ally Warlord using Direct the Strike, and Unleash Spell Power allows them to instead use an arcane at-will attack. As Direct the Strike doesn't specify either "basic melee" or "basic ranged," would they be able to use Blazing Starfall (an Area Burst 1) or Burning Spray (a Close Blast 3), or would they be restricted only to Melee or Ranged powers?

EDIT:
To clarify further: I know replacing a "basic melee attack" means you need to use a Melee power, and replacing a "basic ranged attack" means you need to use a Ranged power. My question is: does replacing simply a "basic attack" mean you're not restricted by what type of power to use, or are you still restricted to either Melee or Ranged, and why?

Answer 1

Yes, in this case you can use an area or close power.

The text of the ability says that it allows targets to use any 1st-level arcane at-will power instead of a granted basic attack. If the granted basic attack is an MBA, then the arcane at-will must be a melee power. If the granted basic attack is an RBA, then the arcane at-will must be a ranged attack.

The power in question grants a basic attack. It does not specify an MBA or RBA, therefore the character being granted the attack may use any arcane at-will, including area and close attacks.

Answer 2

You cannot use Area Burst attacks or Blasts because they are not a Melee or Ranged attacks.

Player's Handbook pg. 270 (emphasis mine):

Targeted: Melee attacks target individuals. A melee attack against multiple enemies consists of separate attacks, each with its own attack roll and damage roll. Melee attacks don't create areas of effect.

Also see the entry on ranged attacks:

Targeted: Ranged attacks target individuals. A ranged attack against multiple enemies consists of separate attacks, each with its own attack roll and damage roll. Ranged attacks don't create areas of effect.

There is nothing in the entries for Burst or Blast attacks to overrule this, so unless you have a specific power that also specifies it is a ranged or melee attack, they are not normally.