Is this going to be a rod for stillwater waggler fishing, river trotting, or a bit of everything? When you say "lighter", do you mean the weight of the rod or the power/action?
You'll struggle to get a lighter weight rod than an Acolyte without a lot of effort and expense. The only rods I've come across that are significantly lighter are by Rive and very difficult to get hold of. I don't recall seeing a hint of them in 15'+.
The Maver Signature Pro Classic is slightly heavier than an Acolyte and well worth shortlisting. They are closer in power to the Acolyte Plus than the Ultra. The snag is that they are discontinued.
Similar story with the Browning Sphere Match rods. Lighter than the Acolytes in the same lengths, discontinued and only in 13/14'. However, if you want a rod purely for trotting, the Browning Sphere Spliced Tip River rods (13'6" or 15'6") are fantastic. I've used them for barbel down to gudgeon and all points between. It's not a rod to put 10lb mainline through though.
Amongst plenty of other float rods, I own and use Acolyte 17' Float, 15' Acolyte Ultra and Plus, Maver Signature Pro Classic 15' and the 15'6" Browning Sphere Spliced Tip River.