I have been thinking about rules a lot recently, since certain quirks have impacted on my gaming. What I thought might be interesting for myself, and others, would be to go through the rules I am using in different periods and where my thoughts are about them...
Ancient & Medieval:
I regularly use three rulesets, Polemos: SPQR, DBA and Neil Thomas' sets. I won't repeat my previous comments about them but will instead concentrate on where one or more of them are failing (for me).
None of these rules is designed to be scalable. DBA and Polemos are aimed at roughly the same size of game, in which a single infantry base represents about 500 troops: handily, a cohort for mid-period armies. This works fine for games of 1-3 legions assuming 8-12 bases per legion, but the games get quite big after that. Not a problem in general, but I run out of space quite quickly: the maximum size of table I can easily use currently is 5'x'3, and it is more typically 6" smaller than that on each side. This may change a bit (for the larger) in the summer. Neil Thomas is more abstract and isn't necessarily supposed to represent any particular unit size, although if one scaled it to the missile ranges, I imagine it would turn out to be a "unit" might be 500-1000 troops or so.
Neil Thomas in all his sets proposes a quite attritional view of combat. Not saying this is wrong, but it seems more suitable for some periods than others: I would think it should increase in importance throughout history.
Anyway, slight concerns about the rules are still delaying my commencement of refighting the Gallic Wars - I have started three times now, and the campaign system works fine, but I just haven't been convinced enough yet about the tactical rules. Maybe Phil Sabin's Lost Battles need another look, but I'm not sure how one would necessarily go about doing an imaginary battle with them.
I think I am most dissatisfied with DBA and NT for Wars of the Roses: nothing about either game seems to really gel with my impressions of Wars of the Roses combat. More broadly, I want to feel like each army I play is commanded differently and with even the vaguest resemblance to how it may have been commanded in real life and I am not convinced that many of the big "Ancient Period 4000BCE-1525CE do that too well". I want to get hold of a copy of Comitatus again, too.
Pike & Shot:
Apart from some slightly powerful artillery in grand battery, the Twilight of Divine Right rules are working for me so far for the Thirty Years' War. For battles of the War of the Three Kingdoms, I don't see much need to change from Polemos: ECW, especially since I am happy with the slight recalibrations I have done.
I am not quite sure where to go here. Much as I like Polemos: Napoleonics and Horse, Foot & Guns - and I really like them both - I have a couple of niggles that I don't see any chance of going away. HFG doesn't really do attrition at all, Polemos only does it in a very partial form but without attrition, it is hard to fight the way that Napoleonic armies fought. That isn't to say that shock action wasn't important too, but without a mechanism for wearing down the enemy, it is hard to make wearing down the enemy a viable tactical choice. I had been thinking of dusting off Grande Armee, although that is a little roster-heavy and a bit fussy. Someone reminded me that Blucher might be a decent alternative option too. Neil Thomas' rules are quick and fun - and I really like his C19 rules and his generic Horse-and-Musket "Simplicity in Practice" rules - but they are somewhat abstract constructs: in certain ways, Maida, Quatre Bras, Austerlitz and Leipzig are all going to feel somewhat samey. This has certain benefits, especially in ease of play, but on the other hand a certain amount fo flavour is lost: commanding a large army of five army corps shouldn't feel the same as commanding a large brigade with a cavalry regiment attached - combat is not fractal. Other rulesets which I have tried and liked in the past are Shako (first edition) and Howard Whitehouse's "Old Trousers". Paul Leniston's rules weren't bad either (although I am not too keen on having brigades in square, column and line, a la Napoleon's Battles), nor were Bob Cordery's Napoleonic rules, although I would have to spend some time re-calibrating the latter in some minor ways to my taste. I still really like Polemos Ruse de Guerre for its scope of action but it is currently designed to top out at 800men/base...perhaps I could fool around with a big battle version of these...I want to give "Morale Napoleon" a go too, since they are designed with solo play in mind.
I still like the WRG 1925-1950 rules for these, although I am thinking of giving second edition a fuller go (I am currently using) first edition. I don't actually have much desire to do much else at the moment, my rules-focus is on improving the Threat Generation System for solo play (although Chain of Command and Troops, Weapons & Tactics are always good). For smaller games, I still love Nuts! although I am going to give Five Men at Kursk a run-out too. For larger games, I am still looking, although my lack of organization has been as much of a problem for really getting into this scale of battle as anything else! I am still very happy with my adaptation of Bob Cordery's rules for air warfare and want to develop these further (although I am still quite partial to Lacquered Coffins as well).
There are always lots of rules I would, in theory, like to try but new rulesets are a big investment in time, which is at a slight premium at the moment, so most of my experimentation will have to wait until 2021 I imagine. One exception is Chrome Hammer - I have a fondness for Cyberpunk, so there is every chance I will make a point of getting that to the table. 2-Hour Dungeon Crawl and Five Leagues from the Borderlands also need more games played.