I'm not a huge fan of using the TWF model of extra attacks as the means for recovering the actions lost by mounting up as opposed to fighting separately. For one thing, it only lets you get back attacks, which although certainly the most prominent kind of action you'd likely want, are far from the only kind. For another, it just doesn't feel right to charge additional penalties (on top of the feat slot) just to get back an action you've already paid for by whatever means you acquired the additional character. Even with the feat not penalizing attacks (as other multiattack feats do), it really raises the question of whether that's really worth the price of that feat being entirely useless unless you're mounted, as opposed to simply taking one of the more standard multiattack feats.
My approach to buying back those actions would be more like so:FIERCE RIDER
[Basic Combat] Benefit:
While part of a mounted pair, when either member of the pair takes a non-Movement or Handle Item half action, you gain an additional half action this round which must be used for a non-Movement or Handle Item action performed by the other member of the mounted pair. You and your partner in the mounted pair may gain only one additional half action per round in this fashion, even if both of you have this feat.MERCILESS RIDER
[Basic Combat] Prereqs:
Fierce Rider Benefit:
You may gain up to two additional half actions per round from your Fierce Rider feat. However, you cannot use an extra half action granted by that feat to trigger its own effect for a second half action. Also, when either member of your mounted pair performs a non-Movement full action, you may expend both uses of your Fierce Rider feat for this round to gain two additional half actions which must be used for non-Movement or Handle Item actions performed by the other member of the mounted pair.
The intent her being essentially that if you take both these feats, you get the same sort of action economy that you'd have under Kingswood Mr Jazz's campaign quality, without needing any fundamental changes to the mounted combat rules. With Kingswood Mr Jazz's approach, barring any additional abilities to grant extra actions, you could:
- Take two movement half actions, or one movement full action (since this counts against the actions of both mount and rider)
- Take one movement half action (counting against both mount and rider's actions), one non-movement half action by the rider, and one non-movement half action by the mount, in any order
- Take two non-movement half actions each as both mount and rider, in any order
Assuming I'm parsing my own rules text right, my feats here would afford the same possible actions per round, just mediated through triggered extra actions:
- Take two movement half actions (consumes both half actions available to a mounted pair, does not trigger feats)
- Take one movement half action (taking one of your baseline actions available without triggering the feat), one non-movement half action by one member (triggering the feat), and one non-movement half action by the other member (granted by the feat), in any order
- Take two non-movement half actions each as both mount and rider, in any order (two half actions from your baseline allotment, triggering two extras granted by the feats, with the feats requiring an even split of actions)