The MOD Prime Links
already incorporates dealing with a link target, so it is already somewhat available for phpBB3.
BTW: I hate link targets which always want to force me being opened in a new container (tab or window) - this is a choice made by the user - he should configure his browser to open links in a new container (tab or window). The target="_blank"
syntax was never valid in strict mode. See http://www.w3.org/TR/WCAG-TECHS/H83.html
The objective of this technique is to avoid confusion that may be caused by the appearance of new windows that were not requested by the user. Suddenly opening new windows can disorientate or be missed completely by some users. In HTML 4.01 Transitional and XHTML 1.0 Transitional, the target attribute can be used to open a new window, instead of automatic pop-ups. (The target attribute is deleted from HTML 4.01 Strict and XHTML 1.0 Strict.) Note that not using the target allows the user to decide whether a new window should be opened or not. Use of the target attribute provides an unambiguously machine-readable indication that a new window will open. User agents can inform the user, and can also be configured not to open the new window. For those not using assistive technology, the indication would also be available from the link text.