LRF have proved to be the problem unit in the development of the game and despite the attempt to suppress them with extra fighters in the first major rebalance, they have continued to proliferate. I suggest another core rebalance for the second expansion to bring the less favoured LF back into the game as counters to LRF, while LRF switch to counters for support. This might also solve problems with powerful support cruisers like Guardians, as LRF have enough hitting power to be effective against support even when being attacked by LF. Finally I'd like early structures to be cheaper to deter the rush, and mines to be reworked with more upgrades.
LRF are far too effective in the game in its present form. They deal high damage to all targets and building the units that counter them creates problems- a scout fleet is too one-dimensional, flak are ineffective on the attack and fighters have to suppress enemy fighters and bombers before they can be used against LRF. What I find particularly odd is that LRF are the heavy hitters of a fleet but are also the main counter to fast agile LF, because they have anti-medium weapons rather than the anti-heavy weapons their role suggests. By the time units that LF are effective against appear, LRF can be present in numbers. LRF are so much of a counter to LF that players are reluctant to use LF even if flak and carriers are being used, possibly because flak and carriers are more durable and LF do too little damage to them.
What I'd suggest is a change in the core balance of the game, so that LRF are moved to anti-heavy weapons and LF to a new category 'light composite'. The anti-heavy weapons could then be buffed to 75% damage against very heavy and capital armour, which seems to make more sense than having anti-medium weapons more effective against those types than anti-heavy. For 'light composite' Light 125% Medium 100% Heavy 75% Very Heavy 50% Capital 50%, the existing LF mix with a buff against Scouts and LRF and a nerf against support.
Under this new system of counters LF would counter LRF, while LRF would counter the heavier units like flak and carriers. LF may lack hard counters- it would help to restore anti-medium to 150% against medium armour so that LF are very vulnerable to turrets again, and also to buff heavy cruisers against LF- composite is light 150% medium 100% and heavy 125% currently, which is a curious progression, how about 125% against medium? It seems acceptable for a unit which hasn't high firepower and isn't as effective against capitals to lack a hard counter until heavies appear.
I would also make turrets and hangars cheaper, both have become progressively less cost-effective as the game has developed. The anti-structure cruisers might then be more valuable. Mines are a problem area and more upgrades may be needed, whether by new techs or pacts or both.
No new combat units seem to be planned for the expansion, however something could be done to prevent the game continuing to be based around LRF spam. If LF were brought fully into the game, and the role of structures and mines enhanced, it would be like having new units even though they were already present.