I have been working on a 15mm Royal English force for ages. I am two elements from maxing out my projected build. The project stalled because I was waiting to see if Khurasan would ever release (officially) their Elizabethan English line, but I need to just finish it off with the Essex I have. I like Essex, but with this period, it is really lacking in character.
Their adversaries will be a (what-if invading) Spanish Expeditionary Force, which I can fill (at least in large part)from Khurasan. I hope to pick up and finish those by the end of the year at (hopefully) the latest.
I am also planning English Adventurers vs. Spanish Colonials, in 28mm. The former will be mostly from Foundry's excellent Swashbucklers line, the Spanish will be mostly Old Glory, with others thrown in.
They will all be skirmish-based for other rules, but I will sabot them with unit bases from Litko, or maybe my own make. The individual skirmish bands (such as for En Garde) are the short-term build, it will be some time before it "maxes out" to IW-level.
I have solo-played with counters, and really like the rules. I hope to make some progress, and post some pics. I'd be happy to see any of yours or anyone else's. And a campaign system sound quite intriguing.