Tensei_Rigan
Pandas seem to be the best option. Also for resolving the clan situation the best idea will be to learn fuinjutsu and make a better seal and presenting it to the clan. When they inevitably try to use caged bird seal on you then attack them and place the old seal on them. Create a mutually assured destruction scenario and force the use of new seal. The other option is to find where all the info of seal is stored and then destroy it and kill everyone who knew it. The new seals will probably not include the caged bird components.
Panda seems more like masters than summons so if possible maybe panda plus koi? Otherwise only panda since among the other option is the more useful (the lion one seems a bad copy of the toad summons).... I also hope he will start to learn fuinjutsu : outside of rinnegan and Sharingan fuinjutsu is the most bull**** deux et machina ability of Naruto verse and with a system and with him being a hyuga and wanting to learn the hiraoshin and Tsunade hundred seal (all based on fuinjutsu) it would be a waste for neji non learning it (even more with the good memory he has and the perfect Chacra control with huge Chacra reserve that he eventually will gain)