I think I can help, but I have a couple of questions first. Is the idea here to
a) escalate issues if and only if they have already been escalated by a specific other escalation?
b) escalate issues despite their having been escalated by another escalation?
If a), the first escalation would need an action that puts a flag in some field that your new escalation could examine and use as part of its criteria.
If b), that's what the "re-escalate" flag is used for, but I understand you don't want to use this flag. Is the reason you don't want to use it that you don't want the age-based escalation to be limited to running at most once on a given issue? If so, then I have something for you...
The way that FootPrints stops an escalation with the "re-escalate" flag from running multiple times on the same issue is by adding the escalation's id# to a hidden issue field called mrESCALATEDBY when the escalation acts on an issue. I have a Perl script that will remove an escalation's id# from the mrESCALATEDBY field making an issue eligible to be acted upon again by that escalation.
So you would first enable the "re-escalate" checkbox on your age-based escalation. Then you would an external action to that escalation following this syntax:
perl mrUnsetEscalatedBy.pl <issue#> <workspace#> <escalation_id> [escalation_id ...]
The issue # and workspace # are discoverable at runtime using %%MRID%% and %%PROJID%% variables. You would hardcode the escalation id, which you can find by highlighting the escalation from the full list of escalations and clicking the "Escalation Summary" button.
Let me know if you think this is going to work out for you and I'll keep going with more details.